Physics II workshop_Part_56

Physics II workshop_Part_56 - momentum is conserved . So,...

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114 Impulse on a tennis ball A tennis ball of mass m = 0.03 kg flies towards a wall with velocity v = 20 m s -1 west. It hits the wall, stops momentarily, and then bounces back with the same speed in the opposite direction. (a) What is the ball’s initial momentum? (b) What ball’s final momentum? (c) What is the impulse? (d) The ball is in contact with the wall for t =0.03 s. What is the average force on the ball during the collision? m r v Before collision m During collision m r v After collision
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115 Car-truck collisions Momentum turns out to be enormously useful in solving problems that involve collisions, even when you don't know the details. Why? Because under very common circumstances, the total momentum of a set of colliding objects will be the same before and after they collide. In other words,
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Unformatted text preview: momentum is conserved . So, considering just 1-D motion for now, we can say m A ,1 v A ,1 + m B ,1 v B ,1 + K + m X ,1 v X ,1 = m A ,2 v A ,2 + m B ,2 v B ,2 + K + m X ,2 v X ,2 where subscripts A, B, C etc label different objects and 1 and 2 refer to times immediately before and immediately after the collision respectively. Now consider the following cases: 1. Car crashes into stationary truck, they stick together The car has mass m = 2000 kg and velocity v 1 = 20 m s-1 . The truck is initially stationary and has mass M =8000 kg. What is the velocity, v 2 , of the tangled wreckage immediately after the collision? Is this an elastic, or inelastic collision (is kinetic energy conserved)? v 1 Before v 2 After...
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Physics II workshop_Part_56 - momentum is conserved . So,...

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