Question

A plywood 3m long, 2m wide, and 0.05m thick floats in water with 2/3 of its volume above the water surface. When a person climbs on it, 2/3 fraction of total volume of the ply is found immersed in water. Find the density of the ply and mass of the person ...... pls guys help..

Answer 1

it is given that plywood is 1/3 immersed in water. and let the volume of plywood is V and density of plywood is 'd'.
=> 1000×(1/3)V×g=d×V×g..................(1)
( where 1000 is the density of water in Kg per meter cube and 'g' is the acceleration due to gravity)
by solving equation (1) we get the density of plywood.
=> d=1000/3.
now the in second situation a man of mass m jumps on it making it immersed 2/3 of its volume. hence ,
1000×(2/3)V×g=(m+1000V/3)g.......(2)
and V is given : 3×2×0.05.
as a result of equation (2) we get mass of man=100Kg.