Physics 101 General Physics
Who am I? Dr. Bruton I may be teaching the remainder of this course for Mr. Carlton. We have similar teaching styles. There will be extra credit. I will “teach to” Mr. Carlton’s test. I will hit the highlights of the chapters with PowerPoint presentations.
Let’s take notes…
Chapter 6 Momentum
Momentum and Collisions This chapter is concerned with inertia and motion. Momentum helps us understand collisions.
Momentum and Collisions Elastic Collisions –objects rebound –e.g. superball Inelastic Collisions –object stick together an usually become distorted and generate heat –e.g. clay ball
Momentum Momentum = mass velocity p = mv Momentum is a vector quantity.
A large truck has more momentum than a car moving at the same speed because it has a greater mass. Which is more difficult to slow down? The car or the large truck?
Large Momentum Examples: –Huge ship moving at a small velocity –High velocity bullet P = m v
Impulse In order to change the momentum of an object you must apply a force over some time interval. Impulse = Force time interval = F t
Impulse and Momentum Impulse = Change in Momentum = Final (mv) - Initial (mv) F t = (mv)
Case 1: Increasing Momentum –Apply a force for a long time. –Examples: Follow through on a golf swing. Pushing a car. FtFt
Case 2: Decreasing Momentum –Apply a force for a long time. –Examples: Air bags in cars. Catching an egg. Boxing, Figure 6.6 Soft collisions, Figure 6.3. FtFt
Case 3: Decreasing Momentum –Apply a force for a short time. –Examples: Boxing Karate FtFt
Conservation of Momentum This means that the momentum doesn’t change. Recall that F t = mv) In this equation, F is the "external force". Internal forces cannot cause a change in momentum.
Examples Conservation of Momentum: If there are no external forces, the total momentum for a system remains unchanged. Example 1: a person sitting inside a car pushing against the dashboard Example 2: a bullet fired from a rifle Example 3: a rocket is space
Example Problems...