## Chapters 7 & 8 Physics Test

##### Created by:

peytonginger  on February 28, 2011

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# Chapters 7 & 8 Physics Test

 Newton's Third Law of MotionNewton's Third Law of Motion states that whenever one object exerts a force on a second object, the second object has equal and opposite force on the first object.
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#### Definitions

Newton's Third Law of Motion Newton's Third Law of Motion states that whenever one object exerts a force on a second object, the second object has equal and opposite force on the first object.
Action and Reaction Forces One force is called the Action Force, and the other is called the Reaction Force. Neither can exist without the other. Equal strength & opposite direction. Occur at the same time.
Friction is Important Someone walking where there is minimal friction, may not be able to exert an action force on the ground. Without an action force, there can be no reaction force, therefore there is no resulting forward motion.
Action & Reaction on Different Masses A given force exerted on a small mass produces a greater acceleration than the same force exerted on a large mass.
Defining Systems Action and Reactions forces do not cancel each other when either of the forces is external to the system being considered.
High Momentum An object can have a large momentum if it has a large mass, high speed, or both.
What is Momentum? Momentum is the mass of an object, multiplied by its velocity. If direction is not important, momentum = mass x speed.
Impulse The quantity force x change in time.
The Greater the Impulse... The greater the impulse exerted on something, the greater the change in momentum will be.
Impulse Changes Momentum When you push with the same force for twice the time, you impart twice the impulse and produce twice the change in momentum.
To Increase the Momentum of an Object.... To increase the momentum of an object, apply the greatest force possible for as long as possible.
Impulse and Time If the change in momentum occurs over a long time, the force of impact is small. If the change in momentum occurs over a short time, the force of impact is large.
Conservation of Momentum The law of conservation of momentum states that, in the absence of an external force, the momentum of a system remains the same.
Is Momentum a Vector Quantity? Momentum is a Vector Quantity because it has both direction AND speed.
Momentum of a System The momentum of a system cannot change unless it is acted on by an external force.
Vocab: Conserved When any quantity in physics does not change, we say it is conserved.
Law of Conservation of Momentum If a system undergoes changes wherein all forces are internal, the net momentum of the system before and after the event are the same.
Elastic Collisions When objects collide without being permanently deformed and without generating heat, the collision is an elastic collision.
Inelastic Collisions A collision in which the colliding objects become connected, distorted, or generate heat during the collision is an inelastic collision.
Finding Velocity After Inelastic Collision Twice as much mass is moving after the collision, so the velocity, vafter, must be one half of 4 m/s.
Significant Figures The significant figures of a number are those digits that carry meaning contributing to its precision.

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