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    Question

    A person standing on a trolley moving in a straight line

    throws a stone vertically upward, relative to himself, while facing in the direction of motion. Which of the following is true?
    A The stone will always land back in his hand. Correct Answer Incorrect Answer
    B The stone will never come back to him. Correct Answer Incorrect Answer
    C If the trolley is accelerating forward, the stone will land behind him. Correct Answer Incorrect Answer
    D The stone will return to his hand only if the trolley moves at a uniform velocity Correct Answer Incorrect Answer

    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.
    Thus, the correct conclusion is: The stone will return to his hand only if the trolley moves at a uniform velocity.

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