Question

33. A truck moving on horizontal road east with
velocity 20ms collides elastically with a light ball
moving with velocity 25 ms-1 along west. The
velocity of the ball just after collision
(A) 65 ms-t towards east
(B) 25 ms 1 towards west
(C) 65 ms 1 towards west
(D) 20 ms-1 towards east​

Answer 1

Answer:

Explanation:Actually the given problem deals with a Truck of a very large mass M and a ball of very light mass m.

M>>>m

So, let the initial velocity of truck u1 be +20 m/s

And the velocity of ball before collision u2 be -25 m/s

( - represents towards west)

So, Use the given formula : $v1 = (m1-m2)/(m1 + m2)u1 + (2 . m2/ m1 + m2)u2

For solving it you can assume the mass of ball m to be negligible, you will get 65 m/s East.

So, we can say when a body of negligible mass collides with another body of a huge mass then the change in the velocity of the huge body is also negligible but the velocity of light object becomes = -(2* times the velocity of large mass + velocity of itself) (- sign represents change in direction)