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. What will be the speed of the ball after ‘elastic’ collision with 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. What will be the speed of the ball after &lsquo;elastic&rsquo; collision with wall ? (A) u+v away from the wall (B) 2u+v away from the (C) |u - v| away from the wall (D) |v - 2 u| away from the wall

Tardigrade Admin · Accepted Answer

From the frame of wall, the ball moves towards the wall with speed u+v and after collision returns with velocity u+v as shown in Figure 1. Then from ground frame, the velocity of ball after collision with wall is 2u+v

Q. 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. What will be the speed of the ball after ‘elastic’ collision with wall ?

$u + v$ away from the wall

$2 u + v$ away from the

$∣ u - v ∣$ away from the wall

$∣ v - 2 u ∣$ away from the wall

From the frame of wall, the ball moves towards the wall with speed $u + v$ and after collision returns with velocity $u + v$ as shown in Figure 1. Then from ground frame, the velocity of ball after collision with wall is $2 u + v$

Q. 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. What will be the speed of the ball after ‘elastic’ collision with wall ?

u+v away from the wall

2u+v away from the

∣u−v∣ away from the wall

∣v−2u∣ away from the wall