Why does a ball inside a moving bus at rest start moving backwards when the bus suddenly accelerates? Also does the moving ball have some acceleration?
This is my theory: Initially the bus and the ball are at rest. When the bus starts accelerating, due to inertia of rest, the ball resists change in motion and tends to remain at rest. Since it is an accelerating frame, pseudo forces of unknown origin act on the ball in the direction opposite to the direction of motion of the bus. This pseudo force is responsible for the ball to move in the opposite direction with some acceleration. This explanation with respect to the accelerating frame.
But how do I explain this fact from the frame of reference of a person on the road? I understand that the acceleration of the ball is in the same direction as that of acceleration of bus. There is no other force to balance this force which is in the direction of motion of bus. So the ball should have moved in a direction along the direction of the bus. But the reverse happens. Please help me.