__Force__

1. A car of mass 1000 kg travelling at 10 m/s stops in 4 s

Calculate a) the average deceleration.

b) the braking force.

2. An aeroplane accelerates uniformly from rest (0 m/s) to 200 m/s in 40 s.

What force does it exert on a pilot whose mass is 90 kg?

3. The valve of a cylinder on an engine containing 12 kg of compressed gas is opened and the cylinder empties in 1min 40 sec. If the gas leaves its chamber at 25 m/s find.

a) the acceleration of the gas.

b) the force exerted on the chamber.

4. A bullet of mass 20 g travelling with a velocity of 300 m/s hits an earth bank and is brought to rest in 0.2 s.

Find a) the deceleration of the bullet.

b) the force it exerts on the earth bank.

5. A car hits a wall and decelerates at 40 m/s

^{2}. It exerts a force of 20 000 N on the wall. What is the mass of the car?6. A stone of mass 0.5 kg falls into a sandpit exerting a force of 5N. What is its acceleration?

7. A car of mass 750 kg stops uniformly in 5s. If its initial velocity was 15 m/s calculate the braking force.