Question

A raft of wood(density=600 kg/m^3) of mass 120 kg floats in water.how much weight can be put on the raft to make it just sink

Answer 1

Let we add a mass m on the raft to make it just sink .Meaning that the volume of raft is now completely immersed in water.
let the volume of raft is V which is given by:
V= (mass of raft)/(density of raft)=0.2 meter cube.
now this volume is completely immersed in water hence the buoyancy provided by water must balance the weight of raft and the extra mass we have just added.
hence,
1000×0.2×g= (m+120)×g.
(where 1000 is the density of water in Kg per cubic meter & g is the acceleration due to gravity .)
solve it for mass.
you will get m=80Kg.

Answer 2

Answer:

The answer should be 80kg