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Byju's Answer

Standard XII

Physics

Relative Acceleration

A block of ma...

Question

A block of mass 2 kg is kept inside a lift. Lift starts moving downward with an acceleration of a = $12 m / s^{2}$ . Height of the lift is 4m. Time after which block will strike roof of the lift is (Take g = $10 m / s^{2}$ )

2 second

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3.5 second

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4 second

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5.2 second

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Solution

The correct option is A
2 second

Block will loose the contact with the lift and starts moving in upward direction w.r.t. the lift.

Apply 1D motion equation for the relative motion, $s_{r e l} = u_{r e l} t + \frac{1}{2} a_{r e l} t^{2} \Rightarrow 4 = 0 + \frac{1}{2} (- 10 - (- 12)) t^{2} \Rightarrow 4 = \frac{1}{2} (2) t^{2} \Rightarrow t = 2 s$

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A block of mass 2 kg is kept inside a lift. Lift starts moving downward with an acceleration of a = $12 m / s^{2}$ . Height of the lift is 4m. Time after which block will strike roof of the lift is (Take g = $10 m / s^{2}$ )

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A block of mass 2 kg is kept inside a lift. Lift starts moving downward with an acceleration of a = 12m/s2. Height of the lift is 4m. Time after which block will strike roof of the lift is (Take g = 10m/s2)

The correct option is A 2 second Block will loose the contact with the lift and starts moving in upward direction w.r.t. the lift. Apply 1D motion equation for the relative motion, srel=urelt+12arel t2⇒4=0+12(−10−(−12))t2⇒4=12(2)t2⇒t=2s

A block of mass 2 kg is kept inside a lift. Lift starts moving downward with an acceleration of a = $12 m / s^{2}$ . Height of the lift is 4m. Time after which block will strike roof of the lift is (Take g = $10 m / s^{2}$ )