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Impulse and Momentum

Learn about inertia, motion, and how momentum helps us understand collisions. Explore elastic and inelastic collisions, large momentum examples, Newton’s Second Law, impulse, and conservation of momentum with practical examples and calculations.

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Impulse and Momentum

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  1. Impulse and Momentum

  2. Momentum and Collisions • The goal with lesson is to understand 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 F = ma F = m(Dv÷Dt) F = (Dmv)÷(Dt) F· ∆t = (Dp) ÷(∆t) ∙∆t Impulse (∆p)=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. Minimize the Force • Increase Dt • Catching a ball • Bungee jumping FDt

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

  10. Conservation of Momentum • This means that the momentum doesn’t change. • Internal forces cannot cause a change in momentum.

  11. m1 m2 m1 m2 Collisions Before After

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

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

  14. Things I Understand…I Need to Know more of…

  15. Conservation in Momentum 1. A 12,000kg. railroad car is traveling at 2m/s when it strikes another 10,000kg.railroad car that is at rest. If the cars lock together, what is the final velocity of the two railroad cars?  2. A 9,300 kg. railroad car traveling at a velocity of 15m/s strikes a second  boxcar at rest. If the two cars stick together and move off with a velocity of 6m/s, what is the mass of the second car? 3. A 25 gram bullet is fired from a gun with a speed of 230m/s. If the gun has a mass of 0. 9kg. What is the recoil speed of the gun? 4. A 20 gram bullet traveling at 250m/s strikes a block of wood that weighs 2kg. With what velocity will the block and bullet move after the collision? Conservation in Momentum

  16. Impulse Impulse=FDt • A rocket engine fires for 10 seconds while providing 4,000 N of thrust. What impulse is given to the rocket by its engines? • A 500-g baseball is given an impulse of 12.5 N-s by a baseball bat. The bat is only in contact with the ball for 0.10 seconds. What is the average force of the bat acting on the ball?

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