Conceptual Physics Notes on Chapter 7 Momentum Momentum

Conceptual Physics Notes on Chapter 7 Momentum

Momentum n Momentum ( p ) is mass of an object times velocity. p = mv n Any object can have a large momentum if that object has a large mass, a large velocity, or both.

Momentum n To change the momentum of any object, you need to change the velocity. To change any velocity you need to apply a FORCE. n But how long that force is applied is important.

Momentum n Force times time is Impulse ( I ) I = Ft n Impulse is applied to momentum so the two expressions can be equated together. Ft = Δmv

Momentum Bouncing: n Bouncing does not necessarily increase impact force. That depends on impact time. Let’s look at some situations.

Momentum n Bouncing makes the time of Impact small…therefore the Force becomes LARGE! I= n F t Can you think of a situation where this could be used and useful?

Momentum n On the other hand…. if the time is LARGE then the FORCE is small. I= n t F Can you think of a situation where this could be used and useful?

Momentum n Lets compare: I= F t I= t F Note: Impulse is the SAME in BOTH cases!

Momentum Conservation of Momentum n Law of momentum states: In the absence of an external force, the momentum of a system remains unchanged. n When the momentum does not change, we say the quantity is conserved.

Momentum Collisions: n In collisions, momentum is conserved as long as no external force acts on the system. Net Momentum Before = Net Momentum After

Momentum Two Types of Collisions: n Elastic - Collision without being deformed or generating heat. (Object don’t stick together) n Inelastic - Collision when object become tangled or couple together. (Objects stick together)