MHTCET 13 Apr 2026 Shift 2 Paper

Concept:Force is the rate of change of momentum, and the change in momentum is doubled because the direction of each ball reverses after striking the wall.Explanation:Take the direction towards the wall as positive.For one ball of mass $m$ and speed $v$, the initial momentum is $p_i = m v$.After reflecting back with the same speed, the final momentum is $p_f = -m v$.Thus, the change in momentum of one ball is $\Delta p = p_f - p_i = -m v - m v = -2 m v$.Its magnitude is $2 m v$.For 100 balls, the total change in momentum is $100 \times 2 m v = 200 m v$.Since this change occurs in time $t$ seconds, the average force exerted on the wall is$$F = \frac{\text{total change in momentum}}{t} = \frac{200 m v}{t}.$$This is the required total magnitude of force exerted by the balls on the wall.Answer:$$\frac{200 m v}{t}$$Correct option: B.