A ball is bouncing elastically with a speed 1m/s between walls of a railway compartment of size 10m in a direction perpendicular to walls. The train is moving at a constant velocity of 10m/s parallel to the direction of motion of the ball. As seen from the ground.
A ball is bouncing elastically with a speed 1m/s between walls of a railway compartment of size 10m in a direction perpendicular to walls. The train is moving at a constant velocity of 10m/s parallel to the direction of motion of the ball. As seen from the ground.
The correct options are
B Speed of ball changes every 10
C Average speed of ball over any 20 interval is fixed.
D The acceleration of ball is the same as from the train
The speed of the ball when travelling in the same direction as that of the train is (10+1)m/s=11m/s. The speed of the ball just after collision is 9m/s in the opposite direction. Thus, it changes after the collision. Time taken by the ball travelling from one end to other to collide =101=10s. Thus, option (b) is correct.
For the first 10 seconds the speed of the ball is 11m/s. For the next 10 seconds the speed of the ball is 9m/s. The total distance covered by the ball is 20m. The total time taken by the ball to do that is 20 seconds. Thus, average speed during these 20 seconds =1m will be uniform for every 20 seconds. Thus, option (c) is correct.
The train is not accelerating itself and is moving with a constant speed. It thus acts as an inertial frame of reference. Earth/ground is also an inertial frame of reference. Thus, the acceleration will be same in both the frames. Option (d) is correct.
B Speed of ball changes every 10
C Average speed of ball over any 20 interval is fixed.
D The acceleration of ball is the same as from the train
The speed of the ball when travelling in the same direction as that of the train is (10+1)m/s=11m/s. The speed of the ball just after collision is 9m/s in the opposite direction. Thus, it changes after the collision. Time taken by the ball travelling from one end to other to collide =101=10s. Thus, option (b) is correct.
For the first 10 seconds the speed of the ball is 11m/s. For the next 10 seconds the speed of the ball is 9m/s. The total distance covered by the ball is 20m. The total time taken by the ball to do that is 20 seconds. Thus, average speed during these 20 seconds =1m will be uniform for every 20 seconds. Thus, option (c) is correct.
The train is not accelerating itself and is moving with a constant speed. It thus acts as an inertial frame of reference. Earth/ground is also an inertial frame of reference. Thus, the acceleration will be same in both the frames. Option (d) is correct.
