Question

A bucket of water contain a wooden block floating in water with(4/5)th of its volume sub merged in the water. The bucket is placed on the floor of a lift and the lift now starts moving down with uniform accleration. The block of wood now

• A. moves upward
• B. moves downward
• C. remains at same place
• D. moves honzontally

Answer 1

Answer: (C)

remains at same place

Answer 2

$\rho_{ s } V g=\rho_{ w }\left(\frac{4}{5} V\right) g \Rightarrow \rho_{ s }=\frac{4}{5} \rho_{ w }$ If effective gravity is changed to $g$ - a; $\rho_{ s } V ( g - a )=\rho_{ w }( xV )( g - a ) \Rightarrow x =\frac{4}{5}$ So, $4 / 5$ th volume of the block is still submerged, thus the block does not move.