Question

a ball of mass 200g falls from a height of 20 m and rebounds to 5m the change in momentum is​

Answer 1

Answer:

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Answer 2

Given,

mass of ball = 200g

height of falling = 20m

height of rebound = 5m

To find,

The change in the moment for the ball.

Solution,

This question can easily be solved easily using equations of motion for free-falling objects.

Let the velocity of the ball just before the collision be $v_1$, and the velocity just after the collision be $v_2$.

When the ball falls from 20m height

$v_2^2 = u^2+2gh$

(where u is the initial velocity and h is the height from which the ball falls.)

⇒$v^2 = 0 + 2 X 9.8 X 20$

⇒$v = 19.8 m/s$

Now when the ball rebounds and goes to the height of 5m,

$v_f^2 = v_2^2 - 2gh'$ (since motion is opposite to the direction of acceleration.)

(where $v_f$ is the final velocity of the ball and h' is the height of 5m.)

⇒ 0 = $v_2^2 - 2 X 9.8 X 5$

⇒ $v_2 = 9.9 m/s$

now the change in momentum here will be,

$mv_1 - mv_2$ = 0.2×19.8 - 0.2×9.9

                 = 0.2 (19.8-9.9)

                 = 0.2 ×9.9

                 = 1.98 kg m/s

∴Change in momentum of the ball = 1.98 kg m/s