A helicopter rises from rest on the ground vertically upwards with a constant acceleration g. A food packet is dropped from the helicopter when it is at a height h. The time taken by the packet to reach the ground is close to [g is the acceleration due to gravity]
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Question

A helicopter rises from rest on the ground vertically upwards with a constant acceleration g. A food packet is dropped from the helicopter when it is at a height h. The time taken by the packet to reach the ground is close to [g is the acceleration due to gravity]

Options

G1 Physics · Accepted Answer

When the helicopter reaches height h, v² = 2gh, so its upward speed is v = √(2gh). After release, the packet satisfies 0 = h + vt - ½gt². Thus t = [v + √(v² + 2gh)]/g = [√(2gh) + 2√(gh)]/g = (2 + √2)√(h/g) ≈ 3.4√(h/g). Hence option D.