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23 Cards in this Set
- Front
- Back
Equilibrium
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-no translational or angular acceleration.
-a system is in equilibrium if the translational velocity of its center of mass and angular velocities of all its parts are constant -the net force acting on a system in equilibrium is ZERO. Fupward = Fdownward Frightward = Fleftward |
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Static equilibrium
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-If all velocities in a system are zero.
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Dynamic equilibrium
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-If any velocities are nonzero, but all velocities are constant.
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Systems not in equilibrium
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-this means that the center of mass is accelerating translationally or its parts are accelerating rotationally.
Steps for facing a problem that is not in equilibrium: 1. write the equations as if the systems are in equilibrium 2. before solving, add 'ma' to the side with less force. |
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Torque
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-a twisting force, a vector but the MCAT allows us to think of torque as clockwise or counterclockwise.
-When the lever arm is used, equation for torque is: T =Fl F = the force applied l = is where the position vector is form the point of rotation to the point where the force acts at 90 degrees. (lever arm) |
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Lever arm
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-a position vector that is from the point of rotation to the point where the force acts at 90 degrees.
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Units of energy
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-Joule
-electron volt |
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Mechanical energy
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-the kinetic energy and potential energy of macroscopic systems.
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Kinetic energy (K)
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-the energy of motion
K = 1/2mv^2 |
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Potential energy (U)
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-the energy of position
-all potential energies are position dependent. |
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Gravitational potential energy (Ug)
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-the energy due to force of gravity
Ug =mgh |
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Elastic potential energy Ue
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-the energy due to the resistive force applied by a deformed object.
Ue = 1/2kdelta(x)^2 k = hooke's law constant for the object x = displacement from the object's relaxed position |
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Law of Conservation of Energy
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-since the universe is an isolated system, the energy of the universe remains constant
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Work
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-the transfer of energy via force
W = Fdcos(theta) where F = force d = displacement of the system theta = angle between F and d |
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Heat
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-the transfer of energy by natural flow from a warmer body to a colder body
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Frictional forces
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-an exception to the work equation because frictional forces change internal energy as well as mechanical energy.
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Equation describing total energy transfer due to forces and none to heat
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W = deltaK + deltaU + deltaEi
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Equation describing total energy transfer due to forces and none to heat or friction
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W = deltaK + deltaU
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Conservative Force
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-mechanical energy is conserved within the system
-When a force acts on a system and the system moves from point A to point B and back, the total work done by the force is zero and it is conservative. -the energy change is the same regardless of the path taken. |
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Law of Conservation of Mechanical Energy
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-States that when only conservative forces are acting, the sum of mechanical energies remains constant.
K1 + U1 = K2 + U2 or 0 = DeltaK + deltaU |
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Nonconservative forces
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-forces that change mechanical energy of a system when they do work
examples: -friction -pushing and pulling of animals W = delta(K) + delta(U) |
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Kinetic frictional forces
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-increase the internal energy of the systems to which they are applied
-does negative work on a sliding box FkD = delta(K) + delta(U) |
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Power
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-Rate of energy transfer
-unit of power is the Watt (W) which is equivalent to J/s. P = delta(E)/t equation for instantaneous power due to a force: P=Fvcos(theta) |