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Question 5227
NEET Physics · Medium

Motion in a Straight Line: Vertical Motion MCQ

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Vertical MotionMediumQuestion 5227

Question

A stone is thrown downward with velocity 10 m/s from a height of 80 m (g = 10 m/s²). Time to reach ground:
  1. A
    (√17 − 1) s
    Correct
  2. B
    4 s
  3. C
    2 s
  4. D
    3 s

Correct answer

(√17 − 1) s

Explanation

Using s=ut+12gt2s=ut+\frac12gt^2 gives 80=10t+5t280=10t+5t^2, or t2+2t−16=0t^2+2t-16=0. Its positive root is t=−1+√17=<strong>(√17−1) s</strong>t=-1+√17=<strong>(√17-1)\text{ s}</strong>, about 3.12 s.

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