question_answer

A block of wood has a mass of 25 g. When a 5g metal piece with a volume of 2 cm3 is attached to the bottom of the block, the wood barely floats in water. What is the volume V of the wood?

A)  28 cc                                    

B)  35 cc

C)  48 cc                                    

D)  12 cc

Correct Answer: A

Solution :

Let volume of wood is V cm3, then total volume of displaced water is (V+2)cm3, then for translational equilibrium, \[(V+2)\rho g=(25g+5g),\] where   all   the quantities are in CGS unit and p is the density of water. \[\Rightarrow \]\[(V+2)\times 1=30\] \[\therefore \]\[V=28c{{m}^{3}}\]