Unit 8
Momentum
Conservation of Momentum illustrated by a collision of two objects
Conservation of Momentum illustrated by a 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", 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".
Collisions
Many homework problems from this chapter are dealing with "collisions".
Rule #1: Total momentum is conserved in all types of collisions. "Conserved" means "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.
Many homework problems from this chapter are dealing with "collisions".
Rule #1: Total momentum is conserved in all types of collisions. "Conserved" means "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.
Reading
BJU book: Ch. 11
Apologia book: Ch. 9
Lab
"Collision Lab"
Homework
BJU book: Ch. 11
Apologia book: Ch. 9
Lab
"Collision Lab"
Homework
| 8.linear_momentum_homework__problems.docx |