Laws of Motion

• Question 533

A ball moving with velocity 2 ms-1 collides head on with another stationary ball of double the mass. If the coefficient of restitution is 0.5, then their velocities (in ms-1) after collision will be 0,1 1,1 1,0.5 0,2

Solution

A.

0,1

If two bodies collide head on with coefficient of restitution

Question 534

A man of 50 kg mass standing in a gravity free space at height of 10 m above the floor. He throws a stone of 0.5 kg mass downwards with a speed 2 ms-1. When the stone reaches the floor, the distance of the man above the floor will be 9.9 m 10.1  10 m 20 m

Solution

B.

10.1

m r = constant

The distance of the man above the floor (total height) = 10+0.1 = 10.1

Question 535

Solution

B.

e1 + 2e2

Question 536

An explosion blows a rock into three parts. Two parts go off at right angles to each other. These two are 1 kg first part moving with a velocity of 12 ms-1 and 2 kg second part moving with a velocity of 8 ms-1.If the third part flies off with a velocity of 4 ms-,its mass would be 5 kg  7 kg 17 kg 3 kg

Solution

A.

5 kg

apply the law of conservation of linear momentum.
momentum of first part = 1 x 12 = 12 kg ms-1
Momentum of the second part  = 2 x 8 = 16 kg ms-1 '
Resultant monmentum
= [(12)2 +(16)2]1/2 = 20 kg ms-1
The third part should also have the same momentum.

Let the mass of third part be M, then
4 x M = 20
M = 5 kg