A-level Physics (Advancing Physics)/Forces and Impulse in Collisions/Worked Solutions

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1. Escape velocity from the Earth is 11.2 km−1. How much impulse must be exerted on a 47000 kg payload to get it to travel away from the Earth?

2. Two billiard balls, of mass 10g, collide. One is moving at 5ms−1, and the other at 2ms−1. After the collision, the first billiard ball is moving backwards at 4ms−1. The collision takes 1 ms. What force was exerted on this ball?

3. What impulse and force were exerted on the second ball?

The impulse was -0.09Ns and the force was -90N.

4. A 60 kg spacewalker uses a jet of gas to exert an impulse of 10Ns. How many times would he have to do this to reach a speed of 1 ms−1 from stationary?

So, the spacewalker would have to do this 6 times to reach a speed of 1ms−1.

5. A 5 kg bowling ball collides with a stationary tennis ball of mass 0.1 kg at 3ms−1, slowing to 2.5ms−1. It exerts a force of 100N on the ball. How long did the collision take?