A ball of mass m moves towards a moving wall of infinite mass with a speed 'v' along the normal to the wall. The speed of the wall is 'u' toward the ball. The speed of the ball after elastic collision with wall is
$u + v$ away from the wall
$2 u + v$ away from the wall
$| u - v |$ away from the wall
$| v - 2 u |$ away from the wall

Question

A ball of mass m moves towards a moving wall of infinite mass with a speed 'v' along the normal to the wall. The speed of the wall is 'u' toward the ball. The speed of the ball after elastic collision with wall is
$u + v$ away from the wall
$2 u + v$ away from the wall
$| u - v |$ away from the wall
$| v - 2 u |$ away from the wall

Toppr Admin · Accepted Answer

In-xA0-the frame of wall- the ball moves towards it with speed u-v and due to momentum conservation velocity-xA0-after collision returns with velocity u-v in the direction in which wall is moving-xA0-So from the ground frame- the velocity of ball after collision with wall is 2u-v-

In the frame of wall, the ball moves towards it with speed u+v and due to momentum conservation velocity after collision returns with velocity u+v in the direction in which wall is moving. So from the ground frame, the velocity of ball after collision with wall is 2u+v.

In the frame of wall, the ball moves towards it with speed $u + v$ and due to momentum conservation velocity after collision returns with velocity $u + v$ in the direction in which wall is moving.
So from the ground frame, the velocity of ball after collision with wall is $2 u + v .$