A balloon starts from rest at ground level and rises with constant acceleration 2 m s⁻². A stone is released from it after 5 s. Taking g=10 m s⁻², the maximum height reached by the stone above the ground is:
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Question

A balloon starts from rest at ground level and rises with constant acceleration 2 m s⁻². A stone is released from it after 5 s. Taking g=10 m s⁻², the maximum height reached by the stone above the ground is:

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G1 Physics · Accepted Answer

At t=5 s, the balloon is at height h = (1/2)(2)(5²)=25 m and its upward speed is v = 2×5=10 m s⁻¹. The released stone rises further by v²/(2g) = 100/20 = 5 m. Therefore maximum height = 25+5 = 30 m.