Question

     A cube of wood having an edge dimension of 20.0 cm

    and a density of 650 kg/m3 floats on water.

    (a) What is the distance from the horizontal top surface

    of the cube to the water level? (b) What mass of lead

   should be placed on the cube so that the top of the

   cube will just level with the water surface?

Answer 1

a) Let the edge of cube be 'a' and required distance be 'x'. Then the volume of cube submerged in water is

Now, applying Archimedes principle, weight of the cube is balanced by buoyant force.

b) Let 'm' mass needs to be placed over. Then, whole cube is in level with water surface.