**Ch. 8: Momentum**

**Ch. 8: Momentum**

__Reading__

*College Physics*, Ch. 8

AP Classroom: Unit 5 "Momentum"

__Topics__

- Momentum is "mass in motion"
- We will study problems involving momentum and various kinds of collisions

__Labs__

- Collision lab

Below: "Conservation of Momentum" as illustrated by the collision of two objects at a picnic, one larger than the other.

__The Big Ideas__

Momentum is "mass x velocity" (p = mv).

Thus, it can be thought of as "mass in motion".

We use the letter "p" for momentum, because the Latin word 'petere' means "to go to", "to attack". It's where we get the words "impetuous, petulant, and impetus"

"Impulse" is a concept Newton came up with to develop his 2nd Law of Motion. We normally write the 2nd Law as "F=ma", but Newton originally expressed it using impulse, as in "Impulse = Change in momentum = force x elapsed time".

From that, you can also say "Impulse = Change in momentum = mass x change in velocity".

Here's a handy chart, below:

__Collisions__

Many homework problems from this chapter are dealing with "collisions".

Rule #1: Total momentum is conserved in all types of collisions. "Conserved" means total momentum "doesn't change".

Rule #2: In an "elastic" collision (perfect billiard balls), both Kinetic Energy

__and__momentum are conserved.

Rule #3: In an "inelastic" collision (billiard balls covered with Velcro), only momentum is conserved. Kinetic Energy is not.

__Collision lab__

I will have instructions for this popular weblab when we get here.

__Homework__

Your homework is hosted in Canvas, along with the due dates.