## Thursday, 22 March 2012

### Force calculations

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/s2.  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.