Concepts Of Physics MCQ Edition [Volume 1]PhysicsCentre of Mass, Linear momentum, Collision
Two friends, Ankit and Bharat, each weighing 40 kg, sit at a separation of d on a frictionless platform. Ankit rolls a 4 kg ball along the platform towards Bharat, who catches it. Bharat subsequently rolls the ball back to Ankit, who catches it. This back-and-forth motion of the ball between the two friends continues. The ball travels at a constant speed of 5 m/s relative to the platform. Calculate the respective spe
Options
- A40 11 m/s, 4 m/s
- B25 11 m/s, 2.5 m/s
- C5 m/s, 50 11 m/s
- D50 11 m/s, 5 m/s
Correct answer
D. 50 11 m/s, 5 m/s
Step-by-step solution
Let the mass of Ankit and Bharat be M = 40 kg each, and the mass of the ball be m = 4 kg. The speed of the ball relative to the platform is v = 5 m/s. Since the platform is frictionless, the net external force on the system (Ankit + Bharat + ball) in the horizontal direction is zero. Thus, the total momentum of the system remains conserved at zero. Let us analyze the change in momentum of Bharat during one round trip: When Bharat catches the ball, he receives a momentum of mv = 4 5 = 20 kg m/s. When Bharat throws t