Question

    A stone thrown upward with a speed ’u’ from the top of the tower reaches the ground with a speed ‘3u’. The height of the tower is-

    A 4u²/g Correct Answer Incorrect Answer
    B 2u²/g Correct Answer Incorrect Answer
    C 6u²/g Correct Answer Incorrect Answer
    D 9u²/g Correct Answer Incorrect Answer

    Solution

    v2 = u2 + 2gh Þ (3u)2 = (-u)2 + 2gh [‘-‘ sign indicates that the direction of stone is against gravity] Þ h = (9u2 - u2)/ 2g    = 8u2/2g Þ H= 4u2/g

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