1 Physics -- Fluid Statics

A piece of cube of wood supporting a 200 g mass just floats in water. When the mass is removed, the cube rises by 2 cm. what is the size of cube?

A piece of cube of wood supporting a 200 g mass just floats in water. When the mass is removed, the cube rises by 2 cm. what is the size of cube?

Let M be the mass of wooden cube and a be the side of the cube.

The body is in equilibrium in both cases. So lets equate the forces in both cases.
Case I:
0.2g+Mg=ρwV1g......(1)

Case II:
Mg=ρwV2g.......(2)

Here, V1=V2+a2.(0.02)V1V2=a2.(0.02)

Now, by subtracting (2) from (1), we get
0.2g+MgMg=ρw(V1V2)g
0.2g=ρwg(0.02.a2)
a2=0.20.02×ρw=101000=0.01 m2a=0.1 ma=10 cm

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