A lift is moving downward at 4 m s⁻¹ when a bolt becomes detached from its ceiling at a height of 45 m above the ground. Taking g = 10 m s⁻², the bolt reaches the ground after:
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A lift is moving downward at 4 m s⁻¹ when a bolt becomes detached from its ceiling at a height of 45 m above the ground. Taking g = 10 m s⁻², the bolt reaches the ground after:

G1 Physics · Accepted Answer

At release, the bolt has downward speed 4 m s⁻¹. Taking downward positive: 45 = 4t + 5t². Thus 5t² + 4t − 45 = 0. Positive root t = (−4 + √916)/10 ≈ 2.63 s, closest to 2.7 s.