2. Momentum Impulse–Momentum Theorem

3. Momentum Objective: For a constant force acting on an object, the impulse by that force is the product of the force and the time the object experiences the force. The impulse also equals the change in momentum of the object.

5. Momentum The sports announcer says, "Going into the all-star break, the Nationals have the momentum." The headlines declare “Washington Redskins Gaining Momentum." The coach pumps up his team at half-time, saying "You have the momentum; use that and bury them in this third quarter." Momentum is a commonly used term in sports. A team that has the momentum is on the move and is going to take some effort to stop. A team that has a lot of momentum is really on the move and is going to be hard to stop. Momentum is a physics term; it refers to the quantity of motion that an object has. A sports team that is on the move has the momentum. If an object is in motion (on the move) then it has momentum.

6. Bill Nye - Video

7. Momentum Momentum can be defined as "mass in motion." All objects have mass; so if an object is moving, then it has momentum - it has its mass in motion. The amount of momentum that an object has is dependent upon two variables: how much stuff is moving how fast the stuff is moving. Momentum depends upon the variables: massmass and velocity.velocity

8. Momentum helps us understand collisions. Momentum is a measurement of “the quantity of motion” of an object. Momentum = mass velocity p = m v Units: kgm/sec (no derived unit) Momentum is a vector quantity. Momentum

9. P = m v Huge ship moving at a small velocity High velocity bullet P = m v Momentum

10. A large truck has more/less momentum than a car moving at the same speed because it has a ________ mass. Which is more difficult to slow down? The car or the large truck? Why? Momentum

11. Momentum Any object with momentum is going to be hard to stop. To stop such an object, it is necessary to apply a Force against its motion for a given period of time.

12. Momentum The more momentum that an object has, the harder that it is to stop. Thus, it would require a greater amount of force or a longer amount of time or both to bring such an object to a halt. As the force acts upon the object for a given amount of time, the object's velocity is changed; and hence, the object's momentum is changed.

13. Momentum If you have watched the sport of football, the defensive players apply a force for a given amount of time to stop the momentum of the offensive player who has the ball. An object with momentum can be stopped if a force is applied against it for a given amount of time.

14. Changing Momentum For an object’s momentum to change, the object must experience an acceleration – i.e. a change in its velocity vector. An object’s change in momentum is proportional not only to the force which causes an acceleration, but also to the amount of time the force acts.

15. Impulse While the net change in momentum is zero for an entire system, each particle can gain or lose momentum individually. The change in momentum is called the Impulse, which is the product of the force and the time interval as already noted.

16. Impulse

17. Newton’s Second Law can read ∑F = ma = m(Δv/Δt) = (mΔv)/(Δt) Where mΔv is equal to Δp, so ∑F = (Δp/Δt) Rearranging we get, ∑ p = mΔv= FΔt = J = Impulse Impulse

18. In a collision, an object experiences a force for a specific amount of time that results in a change in momentum. The result of the force acting for the given amount of time is that the object's mass either speeds up or slows down (or changes direction). The impulse experienced by the object equals the change in momentum of the object. In equation form, F Δt = mΔv Impulse-Momentum

19. Momentum There are two types of collisions. Elastic Collisions - objects rebound Inelastic Collisions - object stick together and usually become distorted and generate heat

20. Apply a force for a long time.  Examples: Follow through on a golf swing. Hitting a baseball. Catching a ball Bungee jumping FtFt Impulse - Momentum

21. Apply a force for a short time.  Examples: Boxing Karate FtFt

22. Impulse - Momentum

23. This means that the momentum doesn’t change. Recall that  F t =  mv), so  F = 0 In this equation, F is the "external force." Internal forces cannot cause a change in momentum. Impulse-Momentum

24. On to problems...

25. A soccer player hits a ball (mass m = 440 g) coming at him with a velocity of 15 m/s. After it was hit, the ball travels in the opposite direction with a velocity of 25 m/s. (a)What impulse acts on the ball while it is in contact with the foot? (b)The impact time is 0.1s. What is the force acting on the ball? Impulse & Momentum

26. A maiden is tied to the rails and you have to save her from a train (100,000 kg) which is approaching at a speed of 30 m/s. You gather all your strength (1000N) and stop the train just in time. 1.What is the momentum of the train? 2.How long did it actually take you to stop the train? Impulse & Momentum

27. Hobo Doc…

28. Application of Forces Frictional Forces