A block is fully submerged in a vessel filled with water by a spring attached to the bottom of the vessel. In equilibrium position spring is compressed. If the vessel now moves downwards with an acceleration `a(lt g)`. What happens to the length of the spring.?

Explanation

When the vessel moves dwonwards, with acceleration, block experiences net pseudo force upwards. Hence apparent weight of the block decreases and the block moves upwards. Hence length of the spring increases. Additional force on the block in upward direciton = pseudo force on the block - decrease in buoyancy force