7 Small Force, Long Contact Time Catching a baseballBungee Jumping
8 Example A cricket ball, mass 0.5 kg, was bowled at 50 m s-1 at a batsman who misreads theball and the 5 kg bat is knocked out ofhis hands, the ball rebounds at 25 ms-1.What is the change in momentum of the ball?If the bat was in contact with the ball for 2.0 ms, how much force did the batsman apply on the ball?
11 Conservation of Momentum Total momentum before is equal to total momentum afterIn a closed system (external forces are negligible)
12 Inelastic Collision (The colliding bodies couple after the collision) Only momentum is conservedPerfectly inelastic collision(The colliding bodies couple after the collision)
13 ExampleA railway wagon travelling at 1.0 m s–1 catches up with and becomes coupled to another wagon travelling at 0.5 m s–1 in the same direction. The faster moving wagon has 1.7 times the mass of the slower one. Immediately after impact, what is the speed of the coupled wagons?
14 Elastic Collision Momentum is conserved. Kinetic Energies are conserved.(Relative Velocities) are conserved.Analyzing billiard ballsSimulation
15 ExampleA trolley of mass 1 kg rolls along a level, frictionless ramp at a speed of 6 m s-1. It collides with a second trolley of mass 2 kg which is initially at rest. The first trolley rebounds at a speed of 2 m s-1.Find, by conservation of momentum, the velocity of the second trolley after the collision.Compare the kinetic energy before and after the collision. Is the collision elastic?
16 ExampleA ball of mass 0.20 kg is dropped from a height of 3.2 m onto a flat surface which it hits at 8.0 m s-1. It rebounds to 1.8 m. (g = 9.8 m s-2)What is the rebound speed just after impact?What is the change in energy of the ball?What momentum change has the ball between just touching the surface and leaving it?