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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.
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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.
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 = mv P = mv
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 = D(mv)
Case 1: Increasing Momentum • Apply a force for a long time. • Examples: • Follow through on a golf swing. • Pushing a car. FDt
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. FDt
Case 3: Decreasing Momentum • Apply a force for a short time. • Examples: • Boxing • Karate FDt
Conservation of Momentum • This means that the momentum doesn’t change. • Recall that F t = D(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