Question

A squash ball, of mass 60 g is thrown towards a wall at a speed of 35m/s .It rebounds off the wall in exactly the opposite direction,at aspeed of 15m/s.
a) Calculate momentum of the ball before the collision with wall.
b) Calculate momentum of the ball after the collision with wall.

Answer 1

Answer:-

a) mass= 60 gram =60/1000=0.06kg.

Momentum before collision =?

Given velocity is 35m/s.

$p = mv$

$p = 0.06 \times 35$

$p = 2.1 \: kg \frac{m}{s}$

so, the momentum before collision is 2.1 kg.m/s.

b)mass= 60 gram =60/1000=0.06kg.

Momentum after collision =?

Given velocity is 15m/s.

But in opposite direction so negative sign should be associated with the velocity I.e.

$v = - 15 \frac{m}{s}$

$p = mv$

$p = 0.06 \times - 15$

$p = - 0.9kg \frac{m}{s}$

so, the momentum after collision is -0.9 kg.m/s.

Magnitude of momentum will give 0.9 kg.m/s.