Ch. 8: Momentum

Reading
Young & Geller, Ch. 8

Topics

• Momentum = "mass in motion"
• Problems involving elastic and inelastic collisions

Labs

• ​Collision lab 

Below: "Conservation of Momentum" as illustrated by the collision of two objects at a picnic.
​Far below: The same principle illustrated by cannon and projectile

Lecture outline
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. 

Lab
"Collision Lab"

Homework
End of chapter problems are hosted in Canvas. Respond to due dates there.