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NEET 2020 (Phase 2) · Motion Under Gravity

Motion Under Gravity question from NEET 2020 (Phase 2)

Q40NEET 2020 · PHASE 2Medium

Motion Under Gravity

A person sitting in the ground floor of a building notices through the window, of height 1.5 m, a ball dropped from the roof of the building crosses the window in 0.1 s. What is the velocity of the ball when it is at the topmost point of the window? (g=10 m/s2g = 10\text{ m/s}^2)

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Answer: (c)

  1. Let vv be the speed at the top of the window: s=vt+12gt2s = vt + \frac{1}{2}gt^2
  2. 1.5=v(0.1)+12(10)(0.1)2=0.1v+0.051.5 = v(0.1) + \frac{1}{2}(10)(0.1)^2 = 0.1v + 0.05
  3. v=1.450.1=14.5v = \frac{1.45}{0.1} = 14.5 m/s
  4. So the answer is (c) 14.5 m/s.
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