Q150S – Impulse and momentum in collisions
(Note: g = 9.8 m s–2)
1.	A powerboat is going at 80 km h-1 when its motor is turned off. In 5.0 seconds its velocity decreases to 50 km h-1. The boat and its passengers weigh 1 tonne.   Calculate the average force exerted on the boat by the combined drag of the air and the water.

2.	In a test of an energy-absorbing bumper, a 1250 kg car is driven into a barrier at 8.0 km h-1.  The duration of the impact is 0.4 seconds and the car bounces back from the barrier at 2.0 km h-1.  Calculate the size of the average horizontal force exerted on the car during the impact

A fragile object dropped onto a hard surface breaks because it is subjected to a large impulsive force. Suppose you drop a 50 g watch from 1.0 m above the floor, and the duration of impact is 0.001 seconds and the watch bounces 5 cm above the floor.  Use arguments based on changes in kinetic and gravitational potential energy to find:
3.	The speed with which the watch hits the floor.

4.	The initial speed of rebound.

5.	The average value of the impulsive force.

6.   A railway wagon travelling at 1.0 m s-1 catches up with and become 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. The slower moving wagon is half-full of liquid in a tank.  Immediately after impact, what is the speed of the coupled wagons?

7.	As a result of the impact the liquid in the part-full wagon sloshes back and forth violently.  Describe the effect this will have on the movement of the wagons. 

8.	A 400 kg satellite travelling at 7.0 km s-1 is hit head on by a 1.0 kg meteorite travelling at 12 km s-1. The meteorite is embedded in the satellite by the impact. By how much is the satellite slowed down?

9.	An American spacecraft mass 18 tonnes docks with a Russian module mass 6.6 tonnes. Assume the relative speed before docking is 0.2 m s-1 and a successful ‘soft’ docking is achieved first time.  Calculate how much faster the combined object is travelling than the original speed of the Russian space vehicle?