A light spring of length 20 cm and force constant 2 N/cm is placed vertically on a table. A small block of mass 1 kg falls on it. The length h from the surface of the table at which the block will have the maximum velocity is :
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Question

A light spring of length 20 cm and force constant 2 N/cm is placed vertically on a table. A small block of mass 1 kg falls on it. The length h from the surface of the table at which the block will have the maximum velocity is :

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G1 Physics · Accepted Answer

Maximum speed occurs when net force is zero, i.e. at spring compression x=mg/k=10/200=0.05 m=5 cm. The spring's natural length is 20 cm, so the block height is 20-5=15 cm. Hence B.