# Physics Review

Notes on Physics

Inertia- tendency of an object to maintain motion. Property of matter. Not newton’s first law. Matter wants to maintain motion- moving objects want to stay in motion if stopped wants to stay stopped. Mass is measure of inertia. Things have mass because they have inertia. Units: kg Symbol m in equation. Inertia is most constantly called rest mass but we call it mass because we are dealing with speeds not going to speed of light.

Kinetic Energy- v^2 is proportional to K (or v is proportional to square root of K) mass is proportional to K K PROPORTIONAL TO MV^2 Kinetic Energy is energy associated with something in motion if it has velocity it has kinetic energy. Energy is scalar. Change in energy can be negative when you go from set energy to loss In collision Units are Joules K=1/2 mv^2 When something is written in speed and you need velocity for equation just square the speed Joules equals kg times m^2/s^2 Velocity has more effect on kinetic energy than mass. Still objects have no kinetic energy. Hint: Energy variables are capital

Momentum proportional to mass and velocity p=mv Units= kg time m/s And is vector in as direction as velocity Conservation laws are applied in closed systems only Collisions are closed Momentum is conserved///// total energy is conserved

Momentum always conserved in collisions thus collision problems are aways momentum problems Total energy is always conserved

Types of collisions:

Elastic collisions

Kinetic energy conserved

Inelastic collisions

Kinetic energy not conserved

Total energy is conserved

Perfectly inelastic collisions

Special case where objects stick together after collisions- follows same rules

Kinetic energy goes into

Deforming object that is colliding heat sound

Change in momentum is impulse

Change in energy is if the energy is gained or lost by a system it is called Work W= change in energy (final- initial) Work can be negative

If work is done on a system it...

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