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Impulse and Momentum

Impulse and Momentum. 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. Momentum.

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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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