Multiple choice

A boy from the roof of a building drops a stone. It takes 1s for the stone to reach the ground. The height of the building is [take g = 9.8 m/s2]

  1. 9.8 m

  2. 4.9 m

  3. 19.6 m

  4. 39.2 m

  5. 3.92 m
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The motion of the body is under gravity. So here, u = 0, a = +g (as acceleration is in the direction of motion, i.e. 9.8 m/s2) t = 1 s Then, equation of motion is h = 1/2 gt2 = 1/2  x  9.8 x 1 x 1 = 4.9 m

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