A cork is submerged in water by a spring attached to the bottom of a pail. When the pail is kept in a elevator moving with an acceleration downwards, the spring length
Medium
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(b) Density of cork $= d$, Density of water $= \rho$
Resultant upward force on cork $ = V(\rho - d)\,g$
This causes elongation in the spring. When the lift moves down with acceleration a, the resultant upward force on cork $ = V(\rho - d)(g - a)$ which is less than the previous value. So the elongation decreases.
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