Presentation is loading. Please wait.

Presentation is loading. Please wait.

Chapter 8 Impulse and Momentum.

Similar presentations


Presentation on theme: "Chapter 8 Impulse and Momentum."— Presentation transcript:

1 Chapter 8 Impulse and Momentum

2 Momentum and Collisions
This chapter is concerned with inertia and motion. Momentum helps us understand collisions. Elastic Collisions - objects rebound Inelastic Collisions - object stick together an usually become distorted and generate heat

3 Momentum Momentum = mass ´ velocity p = mv
Momentum is a vector quantity.

4 Large Momentum Examples
Huge ship moving at a small velocity High velocity bullet P = Mv P = mv

5 Momentum Examples 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?

6 Impulse Newton’s Second Law can read SF = ma = m(Dv/Dt) = (Dmv)/(Dt)
= (Dp/ Dt) Rearranging, Impulse = Dp = FDt

7 When Force is Limited Apply a force for a long time. Examples:
Follow through on a golf swing. Pushing a car. FDt

8 Make it Bounce Dp = p2 - p1 = -p1 - p1 = -2p1 p1 p2 = -p1

9 Minimize the Force Increase Dt Catching a ball Bungee jumping FDt

10 Maximize Momentum Change
Apply a force for a short time. Examples: Boxing Karate FDt

11 Conservation of Momentum
This means that the momentum doesn’t change. Recall that SF t = D(mv), so SF = 0 In this equation, F is the "external force." Internal forces cannot cause a change in momentum.

12 Examples Example 1: a bullet fired from a rifle
Example 2: a rocket in space

13 Collisions Before m1 m2 After m1 m2

14 Inelastic Collisions v = 10 v = 0 M M Before Collision p = Mv v’ = 5 M
After Collision p = 2Mv’ Mv = 2Mv’ v’ = ½ v

15 Elastic Collisions Conserve Energy and Momentum Before Collision
Equal masses Case 1: Case 2: M > M Case 3: M < M

16 Coefficient of Restitution
For perfectly elastic collisions e = 1. If the two object stick together, e = 0. Otherwise 0 < e < 1.

17 Center of Mass

18 On to problems...


Download ppt "Chapter 8 Impulse and Momentum."

Similar presentations


Ads by Google