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127 Cards in this Set
- Front
- Back
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When an increase in speed triples the kinetic energy of a moving object, the magnitude of its momentum
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Increases by a factor of sqrt(3)
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Two objects have masses m1 and m2, respectively. If m2=4m1, and both have the same kinetic energy, which has more momentum (magnitude)?
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Object 2 with mass m2
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A piece of clay with mass m=0.01kg collides with the floor at a speed of 8m/s and sticks. The collision takes 0.02s. The magnitude of the average force the piece of clay experiences during the collision is
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4N
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Assume you are in a car driving and come in contact with this proverbial brick wall. Your car can do 3 things after the strike: it can go through, come to stop, or bounce back. Select the option which will be the most dangerous to you assuming similar collision times.
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Bouncing back
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A ball (mass 0.40kg) is initially moving to the left at 30m/s. After hitting the wall, the ball is moving to the right at 20m/s. What is the impulse the ball receives during its collision with the wall?
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20kg*m/s to the right
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Two balls of putty of equal mass approach each other from opposite directions with equal speeds. They stick together and come to rest. Was momentum conserved in this collision?
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Yes
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You have a mass of 60kg. You are standing on an icy pond, when your “friend” throws a 10kg ball at you with horizontal velocity of 7m/s. If you catch the ball, how fast will you be moving?
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1m/s
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Two particles of masses 2g and 8g are separated by a distance of 6cm. The distance of their center of mass from the heavier particle is
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1.2cm
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A baseball bat with uniform density is cut at the location of its center of mass as shown in the figure. The piece with the smaller mass after the cut is
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The piece on the left
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A radioactive nucleus of mass M moving along the positive x-direction with speed v emits an a-particle of mass m. If the a-particle proceeds along the negative x direction, the center of mass of the system (made of the daughter nucleus and the a-particle) will
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Move along the positive x-direction with speed equal to v
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Suppose you are on a cart, initially at rest on a frictionless, horizontal track. You throw a series of identical balls against a wall that is rigidly mounted to the cart. If the balls are thrown at a steady rate and bounce straight back, is the cart put into motion?
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Yes, it starts to move to the left and steadily gains speed.
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A 55 kg physics student is at rest on a 5 kg sled that also holds a chunk of ice with a mass of 1.5 kg. The student throws the ice horizontally with a speed of 12 m/s relative to the ground. If thesled slides over a frozen pond without friction, how fast (in m/s) are the sled and student traveling with respect to the ground after throwing the chunk of ice?
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0.3 m/s
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A pocket watch and Big Ben are both keeping perfect time. Which minute hand has the larger angular speed ω?
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They both have the same ω.
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Angular speed is measured in units of s-1, which is rad/s. How many degrees correspond to 1 radian?
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1 rad = 57.3 degrees
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A disk is spinning with angular velocity ω as shown. It begins to slow down. While it is slowing, what are the (i) directions of its angular velocity ω (ii) and its angular acceleration α?
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C, D
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A small wheel and a large wheel are connected by a belt. The small wheel is turned at a constant angular speed ωs. How does the angular speed of the large wheel ωL compare to that of the small wheel?
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ωs > ωL
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A student sees the following question on an exam: A flywheel with mass 120 kg and radius 0.6 m, starting at rest, has an angular acceleration of 0.1 rad/s2. How many revolutions has the wheel undergone after 10 s? Which single formula might the student use to answer the question?
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θf = θi + ωi(tf - ti)+ ½ α(tf - ti)2
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F1, F2 and F3 have the same magnitude. Which statement is correct?
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F1 produces the torque with the largest magnitude.
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Both the disk and the ring have the same mass, and the same radius. Which has the larger moment of inertia about the center?
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The ring
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A sphere, a hoop, and a cylinder, all with the same mass M and the same radius R, are rolling along, all with the same speed v. Which has the most total kinetic energy?
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The hoop
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Assume a disk and a ring with the same radius roll down an incline of height h and angle theta. If they both start from rest at t = 0, which one will reach the bottom first?
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The disk
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Some children are riding on the outside edge of a merry-go-round. Ignore friction in the rotation of the merry-go-round. Consider the "system" of the children plus the merry-go-round. At the same time, the children all move towards the center of the merry-go-round. When they do this
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the angular momentum of the system stays constant.
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Substance A has a density of 3.0 g/cm3 and substance B has a density of 5.0 g/cm3. In order to obtain equal masses of these two substances, the ratio VA/VB of the volume of A to the volume of B has to be equal to
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5 : 3.
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Consider three drinking glasses. All three have the same area base, and all three are filled to the same depth with water. Glass A is wider at the top than at the bottom, glass B is cylindrical and so holds less water than A. Glass C is narrower at the top than at the bottom, and so holds less water than B. Which glass has the greatest liquid pressure at the bottom?
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All three have equal pressure at the bottom.
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The brake system in most cars makes use of a hydraulic system. This system consists of a fluidfilled tube connected at each end to a piston. Assume that the piston attached to the brake pedalhas a cross sectional area of one half a square inch and the piston attached to the brake pad has a cross section area of two square inches. When you apply a force of 10 pounds to the piston attached to the brake pedal, the force at the brake pad will be
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40 pounds
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How much negative pressure, with respect to atmospheric pressure, do your lungs have to produce, so you can you suck water through a straw to a height of 8 cm?
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800 Pa
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The density of freshwater is 1 g/cm3 and the density of seawater is 1.03 g/cm3. A ship will float
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lower in freshwater than in seawater.
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A block of wood of uniform density floats so that exactly ¼ of itsvolume is underwater. What is the density of the block?
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250 kg/m3
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Two objects, A and B, have the same volume and are completely submerged in a liquid, although A is deeper than B. Which object, if either, experiences the greater buoyant force?
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Both objects experience the same buoyant force.
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Consider a block of wood floating on water. If you push down on the top of the block until it is completely submerged, the buoyant force on it
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increases.
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Mercury has an unusually large surface tension γ = 0.465 N/m. Calculate the excess pressure inside a drop of mercury 4 mm in diameter.
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465 Pa
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A soap bubble with radius of 3.0 cm is floating in air. What is thepressure difference across the two surfaces of the bubble?The surface tension of soapy water is γ = 69 * 10-3 N/m.
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9.2 N/m2
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Two bubbles are connected by a hollow tube plus a valve. What will happenonce the valve between the two is opened? |
The small bubble will drain into the big bubble.
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Blood and water have the same contact angle with glass. The density of blood is 5% higher than that of water. (ρblood = 1.05 ρwater)While you make your capillary action measurements you find that water rises in the same tube a factor 1.69 higher than a blood sample. The surface tension of water at the same temperature is 0.073 N/m. What is the surface tension of the blood sample?
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0.045 N/m
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Blood flows through a section of a horizontal artery that is partially blocked by a deposit along the artery wall. A hemoglobin molecule moves from the narrow region into the wider region. What happens to the pressure acting on the molecule as it moves from the narrow into the wider region?
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The pressure increases.
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A gardener is watering her garden from a hose. With the water pressure full blast holding the hose horizontally she can just reach a distance of 12 m, but needs to water an area up to 15 m away. By what fraction must she reduce the cross-sectional area of the hose, still keeping the hose horizontal, to be able to water this area?
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1/5
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In your dorm room you watch the Vols play in an out-of-town game. It is a cliffhangers and the winner will be determined in the last few seconds of play. Everybodyis taking their bathroom break right after the game ends. As the toilets flush andhands are washed, the faucet pressure is noticeably reduced, even though the supplypipe to the rooms can carry all the water needed. Why?
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The water has to speed up in the supply pipe and therefore the pressure drops in the pipe.
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When water flows smoothly in a straight hose, its viscosity causes the water to
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convert some of its kinetic energy into thermal energy.
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Two glass marbles of radii r and 2r fall through a high-viscosityfluid. What is the ratio of their terminal velocities vr/v2r?
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¼
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Suppose you work in the E.R. and a choking patient comes in with their trachea obstructed. The diameter is 1/3 of what it was before the obstruction. You manage to correct the problem and send them on their way safely, explaining that such obstructions are particularly dangerous because
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The blocked airway passes only 1/81 the regular amount of air.
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Why can't you get all the dust off your car by just squirting water from a hoseonto it?Why can't you simply remove dust just by blowing across a surface?Why does dust cling to a fast rotating fan?How can a leaf stay on a car moving at high speed?What is one common answer to all these questions?
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This is a consequence of the formation of stationary boundary layer.
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Which of the following three nozzles could be substituted toachieve a streamline flow (R < 2000)?
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Tube I and III
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Compare the flight of two golf balls given the same impulse by the club. Which ballwill travel a larger distance?
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The dimpled ball
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Determine the character of the collision. The masses of the blocks, and the velocities before and after are given.
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The collision is not possible because momentum is not conserved.
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An intravenous blood plasma drip enters a vein in the patient’s arm from a bag raised a height h above the vein. If the diameter of the 5 cm long needle is 0.5 mm, use Poiseuille's law to find the height h that results in a 5 cm3/min flow rate.(Assume the blood pressure in the arm is 18 torr = 2392 Pa and the viscosity of the blood plasma is 1.5*10-3 Pa-s.)
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0.66 m
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Consider two masses, each of size 2m at the ends of a light rod of length L with the axis of rotation through the center of the rod. The rod is doubled in length and the masses are halved. Compare IA and IB.
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IA < IB
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When the body requires an increased blood flow rate in a particular organ or muscle, it can accomplish this by increasing the diameter of arterioles on that area. By what factor must the diameter of an arteriole increase to double the volume flow rate of blood, all other factors remaining the same?
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1.19 |
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Compared to a gear tooth on the rear sprocket (on the left, of small radius) of a bicycle, a gear tooth on the front sprocket (on the right, of large radius) has
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the same linear speed and a slower angular speed.
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You can balance a broom on your hand if you’re careful. To do this trick well, you must look at
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the broom’s center of gravity.
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A scuba diver descends to a depth of 20 m. At that depth, the pressure is approximately
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three times atmospheric pressure.
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You can chew through very tough objects with your incisors because they exert a large force on the small area of a pointed tooth. What pressure in MPa can you create by exerting a force of 500 N with your tooth on an area of 1.00 mm2? Enter an integer.
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500 MPa |
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A fan rotating with an initial angular velocity of 1000 rev/min is switched off. In 2 seconds, the angular velocity decreases to 200 rev/min. Assuming the angular acceleration is constant, how many revolutions does the blade undergo during this time?
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20 |
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It is correct to say that impulse is equal to
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the change in momentum.
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A boat floating in a lake contains a block of volume V0. The density of the block is 5000 kg/m3. If the block is thrown overboard, the volume of the water displaced by the block is
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V0.
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A 104 N car is lifted by a manually operated hydraulic lift. The area of the shaft of the lift is 80 cm2; the area of the piston that forces liquid into the system is 2 cm2. What minimum force must be exerted on this piston to lift the car?
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250 N
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An object is dropped from rest at t = 0 into a viscous fluid. Which of the following best describes the object’s speed as a function of time?
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(b)
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A 40 kg child standing on a frozen pond throws a 0.5 kg stone to the east with a speed of 5 m/s. Neglecting friction between the child and the ice, what is the recoil velocity of the child?
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0.0625 m/s west
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A person sips a drink through a straw. At which of the following three positions is the pressure lowest?
I. Inside the person's mouth II. At the surface of the drink III. At the bottom of the drink |
only at position I
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A block and a rod are joined together. Each object is of uniform density. The center of mass of the combined object is at the position shown by the “X.”Which has the greater mass, the block or the rod?
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The block has the greater mass.
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During a football game the ball is kicked and it travels across the field. If the ball is kicked away from its center of mass it will
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have translational and rotational motion.
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An object rotates initially with a period of 1.0 s. It accelerates with constant angular acceleration for 10 s. Its final rotation period is 0.1 s.What was the magnitude of its angular acceleration?
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5.65 rad/s2
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An ideal, non-compressible fluid is used in the system of pipes shown below. The cross sectional area of pipe 1 is 4 m2, that of pipe 2 is 3 m2, and that of pipe 3 is 2 m2. The fluid enters pipe 1 at 2 m/s, and leaves pipe 2 at 3 m/s. What is the speed of the fluid in pipe 3 and in which direction does it flow?
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The fluid leaves pipe 3 (downward) with speed 0.5 m/s.
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A 90 kg man and a 10 kg girl are initially 10 m apart. They are connected by a massless rope, and are sitting on a frictionless horizontal surface. The man pulls on the rope until they meet. Where do they meet?
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1 m away from the initial position of the man.
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A horizontal pipe, 10 cm in diameter, has a smooth reduction to a pipe 5 cm in diameter. If the pressure of the water in the larger pipe is 8.00*104 Pa and the pressure in the smaller pipe is 6.00*104 Pa, what is the flow speed of the water (in m/s) in the smaller pipe?
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6.53 m/s
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Blood and water have the same contact angle with glass. The density of blood is 5% higher than that of water. (ρblood= 1.05 ρwater)While you make your capillary action measurements you find that water rises in the same tube a factor 1.69 higher than a blood sample. The surface tension of water at the same temperature is 0.073 N/m. What is the surface tension of the blood sample?
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0.045 N/m
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Consider two carts, of masses m and 2m, at rest on an air track. You push on each cart for 3 s, exerting equal force Fnet on each.
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After the push, the momentum of mass m is the same as the momentum of mass 2m.
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A 50 kg woman balances on one heel of a high-heel shoe. If the heel is circular with radius 0.5 cm, what pressure does she exert on the floor?
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6.2 MPa
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During a July 4th firecracker party, a pop bottle rocket lying still on the ground explodes, sending fragments everywhere. If the momentum of the pop bottle rocket (ignore friction!) initially at rest is conserved during an explosion, what can be said about the kinetic energy of various fragments after the collision?
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The total kinetic energy afterwards is greater than what it was initially.
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Detergents or wetting agents
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reduce the angle of contact.
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Suppose you have an aquarium. You have a solid plastic decoration and a rock of about the same volume but the rock has twice the mass. Both are totally submerged in the water. The buoyant force on the plastic object is about
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the same as that on the rock.
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One kilogram of iron (density ~7.8 gm/cm3) and 1 kilogram of aluminum (density ~2.7 gm/cm3) are dropped into a pool. Which is acted on by the largest buoyant force?
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the aluminum
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A 5.00 kg mass sliding along a horizontal frictionless surface at 2.00 m/s collides with a 1.00 kg stationary mass. After the collision the two masses stick together and contact a light Hooke's-law spring with spring constant k = 1000 N/m. What is the maximum compression (in m) of the spring?
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0.13 m
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Consider a rod of uniform density with an axis of rotation through its center and an identical rod with the axis of rotation through one end. Which has the larger moment of inertia about its axis of rotation?
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Rod B with the axis through one end.
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Consider the earth spinning from west to east on its axis. It is slowing down in its rotation due to friction with the air. Using the right hand rule, in what direction is the frictional torque?
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N pole to S pole
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Blood is called a complex fluid because
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its viscosity depends on the velocity of the flow,
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A CD spins at 5500 rpm (revolutions per minute). What is its angular speed in units of rad/s or s-1?
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576
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Flowing honey is less likely to become turbulent than flowing water because
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honey’s large viscosity favors laminar flow
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Two identical carts labeled A and B are initially resting on an air track. The coordinate system for describing the system is shown. The cart on the right, cart B is given a push to the left and is released. The clock is then started. At t = 0, cart B moves in the direction shown with a speed v0. They hit and stick to each other. The graphs below describe some of the variables associated with the motion as a function of time. For the experiment described and for each item in the list below, identify which graph is a possible display of that variable as a function of time assuming a proper scale. "The system" refers to carts A and B together.
(i) the momentum of cart A (ii) the momentum of cart B (iii) the total momentum of the system (iv) the total kinetic energy of the system |
(i) #1, (ii) #3, (iii) #6, (iv) #2
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Two blocks of mass M and 3 M are placed on a horizontal frictionless surface. A light spring is attached to one of them, and the blocks are pushed together with the spring between them. A cord holding them together is burned, after which the block of mass 3 M moves to the right with a speed of 5 m/s. What is the speed of the block of mass M?
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15 m/s to the left
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A 1.7 kg toy car moving in the positive x direction with speed 3.5 m/s hits a toy car of equal mass moving in the positive y-direction with speed of 5.2 m/s. If the collision is perfectly inelastic, calculate the speed of the cars (in m/s) right after the collision.
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3.1
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Two carts on an air track are pushed towards each other. Initially, cart 1 moves in the positive x direction and cart 2 moves in the negative x direction. They bounce off each other elastically. The graphs at the right describe some of the variables associated with the motion as a function of time. For the experiment described and for each item in the list below, identify which graph is a possible display of that variable as a function of time. If none apply, choose N (for none). (i) the momentum of cart 1 (ii) the position of cart 1. (iii) the position of cart 2.
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(i) D, (ii) B, (iii) N
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A 2 kg mass is at x = 0 m, y = 2 m, and a 3 kg mass is at x = 2 m, y = 0 m. The x- and y-coordinates, respectively, of the center of mass of this system are
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6/5 m, 4/5m
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The graph shows the acceleration of a cart with mass m = 0.555 kg, moving initially with constant speed, as a function of time, as a force F = ma stops the cart. Estimate the initial momentum of the cart in units of kgm/s.
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~0.6
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A car moving at 8 m/s crashes into a wall and stops in 0.26 s. Calculate the force (in N) the seat belt exerts on a passenger in the car to bring him to a halt. The mass of the passenger is 64 kg.
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1,969
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A 50 g meter stick lies on the x-axis with its left edge (the 0 cm mark) at the origin. A 61 g mass is attached to the stick at x = 80 cm and a 18 g mass is attached at x = 14 cm. Find the x-coordinate of the center of mass of the system in cm.
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59.2
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Modeling a meter stick as a forearm, compare the force FB that the biceps has to exert to keep the forearm horizontal to the weight of the forearm FW = mg. Let d = 10 cm and the distance from where the biceps muscle attached to the center of mass be d' = 40 cm.
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FB = 5 mg
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The moment of inertia of a meter stick of length L = 100 cm and mass m = 50 g about a perpendicular axis through its center is mL2/12.Two 64 g masses are attached to the stick, at 29 cm to either side of the center. What is the moment of inertia of the system in units of kg cm2 about the perpendicular axis through the center of the stick?Enter an integer.
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14
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A man jumps off of a bridge towards a river below. As he falls, he feels himself spinning forward (clockwise in diagram). To keep from hitting the water head-first, the man should
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windmill his arms clockwise to keep upright.
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Suppose you are riding on a merry – go – round and you move out to the edge. What happens to the rotational rate of the system?
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It decreases because angular momentum is conserved and the moment of inertia increases.
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The angular acceleration of a object with moment of inertia 35 kg m2 about an axis is α = 1.9 s-2.A force is applied a distance 0.12 m from the axis, making an angle θ = 34 degree with the lever arm. What is the magnitude of this force in N?
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99
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A bicycle's wheels have a radius of 33 cm. The bicycle is traveling at a speed of 6.5 m/s. What is the angular speed of the front tire?
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19.7 rad/s
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A centrifuge in a medical laboratory rotates at an angular speed of 3600 rev/min. When switched off, it rotates 50 times before coming to rest. What is the constant angular acceleration of the centrifuge?
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-226.2/s2
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In soap box car races, the cars are boxes with wheels. They begin at rest at the top of a hill, and at the start of the race they all begin rolling down the hill. The soap box car that reaches the bottom of the hill first is the winner. You have entered a soap box car race where the rule is that all the wheels and cars must have equal mass. Since you have taken Physics, you know that it is worse to have wheels with spokes (where the mass is mostly on the rim) rather than solid wheels because
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Given the same torque, the wheels with spokes have a higher rotational mass or moment of inertia and therefore will have a smaller angular acceleration.
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A beaker is filled with water to the rim. Gently you place a toy duck in the beaker and some of the water spills out. The duck floats. The weight of the beaker with the duck floating in it is
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the same as its weight before adding the duck.
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A beaker containing 5.0 kg of water is on a weighing scale. A 0.8 kg block of metal that has density 8*103 kg/m3 that is attached to a string is lowered completely into water without touching the bottom. Assume that the beaker is massless, and water has density 103 kg/m3, and g = 10 m/s2.What is the reading on the scale?
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51 N
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Two fluids have the same contact angle with glass. The density of fluid 1 is larger than the density of fluid 2 . (ρ1 = 1.23 ρ2) The surface tension of fluid 1 is larger than that of fluid 2. (γ1 = 1.58 γ2) Find the ratio h1/h2 of the heights to which a liquid will rise through capillary action in the same capillary tube.Enter a number with 2 digits being the decimal point.
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1.2
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Mercury has an unusually large surface tension γ = 0.465 N/m. Calculate the excess pressure inside a drop of mercury 4 mm in diameter.
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465 Pa
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The picture below shows 5 blocks. The blocks have equal volumes but different masses. The blocks are placed in an aquarium tank filled with water and blocks 2 and 5 come to rest as shown in the figure.Which answer is correct?
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Block 3 will come to rest in the same position as block 5.
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A certain pump can exert a negative gauge pressure of 13.4 kPa. It is used to suck a liquid out of a bucket up a thin pipe. A 8.5 m column of the liquid exerts a pressure of 100 kPa.To what maximum height ( in m) can the the liquid be sucked up the pipe by this pump?
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1.1
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A 2 kg block of wood is floating in water. What is the magnitude of the buoyant force acting on the block?
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19.6 N
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In a stationary homogeneous liquid near the surface of Earth, which of the following is true?
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Pressure is the same at all points at the same height.
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What is the magnitude of the momentum of a fly if it is traveling with speed 1 m/s and has a mass of 0.0001 kg?
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0.0001 kgm/s.
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A bullet is accelerated down the barrel of a gun by hot gases produced in the combustion of gun powder. What is the average force exerted on a 0.03 kg bullet to accelerate it to a speed of 600 m/s in a time of 2.00 ms (milliseconds)?
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9*10^3 N.
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An object that has a small mass and an object that has a large mass have the same momentum p. Which object has the largest kinetic energy?
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The object with the larger mass has the smaller kinetic energy.
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An object that has a small mass and an object that has a large mass have the same kinetic energy. Which mass has the largest magnitude of momentum p?
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The object with the larger mass has the larger momentum p.
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A car is stopped for a traffic signal. When the light turns green, the car accelerates, increasing its speed from 0 to 5.2 m/s in 0.832s. What linear impulse and average force does a 70 kg passenger in the car experience?
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437.5 N in the x-direction.
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A 3 kg steel ball strikes a wall with a speed of 10.0 m/s at an angle of 60o with the surface. It bounces off with the same speed and angle. If the ball is in contact with the wall for 0.2 s, what is the average force exerted on the ball by the wall?
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259.8 i
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A car moving at 10 m/s crashes into a tree and stops in 0.26 s. Calculate the force the seat belt exerts on a passenger in the car to bring him to a halt. The mass of the passenger is 70 kg.
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-2692.3 N.
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If two objects collide and one is initially at rest, is it possible for both to be at rest after the collision? Is it possible for one to be at rest after the collision?
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In collisions between two objects momentum is conserved. Since the initial momentum is not zero, the final momentum is not zero. Both objects cannot be at rest.It is possible for one of the objects to be at rest after the collision. For example, if the masses of the two objects are equal, then after a head-on elastic collision the object initially at rest is moving and the object initially moving is at rest.
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A 10 g bullet is stopped in a block of wood (m = 5 kg). The speed of the bullet-wood combination immediately after the collision is 0.6 m/s. What was the original speed of the bullet?
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300.6 m/s
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Two cars of equal mass and equal speeds collide head on. Do they experience a greater force if the collision is elastic or perfectly inelastic and they stick together?
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If the collisions last about the same amount of time, then the average force experienced by the car is twice as large in the elastic collision.
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A 90 kg fullback running east with a speed of 5 m/s is tackled by a 95 kg opponent running north with a speed of 3 m/s. If the collision is perfectly inelastic, calculate the speed and the direction of the players just after the tackle.
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heir direction of travel makes an angle θ = 32.34o with the x-axis. (The x-axis is pointing east.)
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A 30,000 kg freight car is coasting at 0.850 m/s with negligible friction under a hopper that dumps 110,000 kg of scrap metal into it. What is the final velocity of the loaded freight car?
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0.182 m/s.
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After a completely inelastic collision between two objects of equal mass, each having initial speed v, the two move off together with speed v/3. What was the angle between their initial directions?
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The angle between their initial directions is 2θ = 141o.
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The mass of the blue puck is 20% greater than the mass of the green one. Before colliding, the pucks approach each other with equal and opposite momenta, and the green puck has an initial speed of 10 m/s. Find the speed of the pucks after the collision, if half the kinetic energy is lost during the collision.
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5.89 m/s.
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Four objects are situated along the y-axis as follows: a 2 kg object is at +3 m, a 3 kg object is at +2.5 m, a 2.5 kg object is at the origin, and a 4 kg object is at -0.5 m. Where is the center of mass of these objects?
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The total mass of the system is M = (2 + 3 + 2.5 + 4) kg = 11.5 kg.yCM = (2 kg * 3 m + 3 kg * 2.5 m + 2.5 kg * 0 m - 4 kg * 0.5 m)/(11.5 kg) = 1 mxCM = zCM = 0
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A uniform carpenter's square has the shape of an L, as shown in the figure. Locate the center of mass relative to the origin of the coordinate system.
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The CM of the system lies outside of the system. For irregular-shaped objects it is quite common for the CM to lie outside the system. This special point outside the system responds to external forces as if the total mass of the system were concentrated there.
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The mass of the Moon is 7.35*1022 kg and the mass of the Earth is 6.00*1024 kg. The distance between the Moon and the Earth is 3.80*105 km.Choose your coordinate system so that the center of the Earth is at the origin and the center of the Moon is on the x-axis at x = 3.80*108 m. Calculate the location xcm of the center of mass of the Earth-Moon system
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4600 km.
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The first stage of a Saturn V space vehicle consumes fuel at the rate of 1.5*104 kg/s, with an exhaust speed of 2.6*103 m/s relative to the body of the vehicle. (a) Calculate the thrust produced by these engines.(b) Find the initial acceleration of the vehicle on the launch pad if its initial mass is 3*106 kg.
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3.2 m/s2 upward., 9.6*106 N.
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In the previous problem the rocket expels exhaust gas at a constant rate with constant speed relative to the rocket body. This produces a constant force Fthrust in the forward direction on the body of the vehicle. Does the speed of the vehicle increase at a constant rate?
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No! Ftot = ma = constant. But in this problem m is not constant.
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What is the magnitude of the angular velocity, ω, of the second hand of a clock? What is the direction of ω as you view a clock hanging vertically? What is the magnitude of the angular acceleration of the second hand?
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The second hand of a clock goes through an angular displacement of 2π in one minute. Its angular speed is ω = 2π/(60 s) = 0.105/s. The direction of ω is perpendicular to the face of the clock, pointing into the face of the clock. The average angular acceleration of the second hand is zero.
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What is the average angular speed, in radians per second, of(a) the Earth in its orbit about the Sun, and(b) the Moon in its orbit about the Earth?
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2*10-7/s., 2.7*10-6/s.
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An airliner arrives at the terminal and the engines are shut off. The rotor of one of the engines has an initial clockwise angular speed of 2000 rad/s. The engines rotation slows with an angular acceleration of magnitude 80 rad/s2.(a) Determine the angular speed after 10 s.(b) How long does it take the rotor to come to rest?
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2000/s., 25s is the time it takes the rotor to come to rest.
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A rotating wheel requires 3 s to rotate 37 revolutions. Its angular velocity at the end of the 3 s interval is 98 rad/s. What is the constant angular acceleration of the wheel?
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13.67/s2
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If a car's wheels are replaced with wheels of a larger diameter, will the reading of the speedometer change?
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The sensor for the speedometer senses the angular speed of the wheel.
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A car accelerates uniformly from rest and reaches a speed of 22 m/s in 9 s If the diameter of a tire is 58 cm, find
(a) the number of revolutions the tire makes during this motion, assuming no slipping, and (b) the final rotational speed of the tire in revolutions per second. |
54.3., 12/s.
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The four particles in the figure on the right are connected by rigid rods. The origin is at the center of the rectangle. Calculate the moment of inertia of the system about the z-axis.
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143 kgm2.
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