A person standing on a trolley moving in a straight line

Solution

When the person throws the stone vertically upward relative to himself , it means the stone initially has both a vertical velocity (from the throw) and a horizontal velocity equal to that of the trolley (since both the person and the stone were moving with the trolley before the throw).

• If the trolley moves with uniform velocity , there is no horizontal acceleration , so the stone maintains its horizontal motion and follows a vertical path relative to the person , landing back in his hand.
• However, if the trolley is accelerating forward , the stone—once released—is no longer in contact with the trolley and does not accelerate with it. So the trolley moves ahead during the stone’s flight, and the stone appears to fall behind the thrower.