Q.

If a stone dropped from the top of a tower travels half of the height of the tower during last second of its fall, the time of fall is (in seconds)

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a

3+2

b

2-2

c

2+2

d

4+2

answer is D.

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Detailed Solution

When a stone is dropped from the top of a tower, it falls freely under gravity. Let's solve the problem step by step.

  1. The height H of the tower is determined by the formula:

    H = (1/2) g t^2
     

    This is because a stone dropped from the top of a tower falls with initial velocity u = 0.

  2. The distance covered by the stone in the last second is:

    (1/2) g (2t - 1)
     

    Since a stone dropped from the top of a tower travels half of the tower's height in the last second:

    (1/2) g (2t - 1) = (1/2) [(1/2) g t^2]
     
  3. Solving this step-by-step, we get the quadratic equation:

    t^2 - 4t + 2 = 0
     
  4. Using the quadratic formula, we find:

    t = 2 + √2 seconds (≈ 3.41 seconds)
     

Thus, the total time of fall is approximately 3.41 seconds.

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