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56 Cards in this Set
- Front
- Back
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How is a frame of reference used to describe motion?
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A frame of reference is used to describe the motion of an object relative to reference points, which are objects that stay in place ( you use them to compare an object in motion )
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What is the deference between speed and velocity?
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everything is the same except that velocity has direction
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What is the equation for speed?
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v=d/t
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What is motion?
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an object's change in position relative to a reference point
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What is a frame of reference?
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a system for specifying the precise location of objects in space and time
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What is displacement?
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the change in position of an object
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What is instantaneous speed?
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speed measured in an infinitely small time interval
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What changes when an object accelerates?
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the object's velocity
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What is the equation for acceleration?
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a=vf-vi/t
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What is acceleration?
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the rate at which velocity changes over time; an object accelerates if its speed, direction, or both change
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When slowing down, is acceleration positive or negative?
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negative
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When graphing acceleration, what are the variables?
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distance vs. time
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What are the fundamental forces of nature?
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gravity, electromagnetic force, strong and weak nuclear force
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What happens when there is a net force acting on an object?
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the object accelerates in the direction of the net force
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What is a net force?
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the combo of all the forces acting on an object
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What force always opposes motion?
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friction
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What is force?
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any action that can change the state of motion of an object
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What is friction?
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a force that opposes motion between two surfaces that are in contact
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What is static friction?
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the friction between unmoving surfaces
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What is kinetic friction?
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the friction between moving surfaces
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Do balanced forces change motion?
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no
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Do unbalanced forces cancel out completely?
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no
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Which is greater - static or kinetic friction?
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static
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What are the subunits of kinetic friction?
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sliding and rolling friction
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What are lubricants?
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things that lower friction - like salt on icy roads
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What makes an object speed up, slow down, and change direction?
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net force
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What determines how MUCH an object speeds up or slows down?
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unbalanced force
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What is inertia?
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the tendency of an object to resist a change in motion unless an outside force acts on the object
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What is Newton's first law?
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An object at rest and an object in motion maintains its velocity unless it experiences a net force
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What does inertia depend on?
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an object's mass
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What is Newton's second law?
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the unbalanced force acting on an object equals the object's mass times its acceleration
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What is the net force equation?
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F=ma
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What unit is force measured in?
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newtons ( N )
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What is the equation for acceleration?
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a=F/m
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What is the difference between mass and weight?
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mass is how much and weight is the measure of gravity
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What are the units for measuring weight?
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newtons ( N )
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What is weight?
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a measure of the gravitational force exerted on an object
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What is free fall?
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the motion of a body when only the force of gravity is acting on the body
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What is terminal velocity?
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the constancy velocity of a falling object when air resistance is equal to the force of gravity ( it stops accelerating )
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What is projectile motion?
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the curved path that an object follows when thrown
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What is the equation for weight?
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w=mg ( g is free - fall acceleration )
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What is ALWAYS the free - fall acceleration?
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9.8 m/s2
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What is the universal gravitation equation?
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F=G(m1m2/d squared)
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As gravitational force increases, mass _____.
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increases
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As distance increases, gravitational force ______.
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decreases
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Why is free-fall acceleration constant?
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because of the law of universal gravitation
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Why is there less gravitational force in space?
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because you are very far form any other massive objects ( all objects attract each other through gravitational force )
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Why do things curve when they are thrown?
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because the object has a horizontal and vertical component so they balance each other out
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Why are people in free fall while their shuttles are in orbit?
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because the shuttle is being pulled toward earth, so if it weren't moving forward, it would go straight down
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What happens when an object exerts a force on another object?
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the second object exerts a force equal in size and opposite in direction on the first object
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What is the equation for momentum?
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p=mv
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What are the units for momentum?
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( kg ) ( m/s ) direction
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What is Newton's third law?
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for every action force, there is an equal and opposite reaction force
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Why don't forces always have equal effects?
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because forces in a force pair do not act on the same object ( ex: a ball falls to earth. Earth's mass is so much more, so the ball's acceleration is MUCH more - but with a ball hitting a flying tennis racket, it goes much higher because the tennis racket's accelerations is a lot more than Earth's )
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What is momentum?
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a quantity defined as the product of the mass and velocity of an object
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Momentum increases as ____ and ____ increase.
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mass, velocity ( like a heavier sledder goes faster down the hill )
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