Question

A wooden block immersed partially into water. There were 15% of the total volume of the block

Answer 1

Density of wooden block is 850 kilogram per cubic meter

Solution:

Given that wooden block immersed partially into water

There were 15% of the total volume of the block  exposed and 85% of the total volume immersed in water

To find: density of the wooden block

The upward force exerted by any fluid upon a body placed in it is called buoyant force

Buoyant force is balanced by weight force of block

Buoyant force is weight of water displaced by block

Buoyant force = $\rho_{w} V_{2} g$

Density of water = $\rho_w$ = 1000 kg/m3

$V_2$ = volume of block in water = 0.85 V

$V_1$ = Volume of block in air = 0.15 V

Weight of block = $\rho V g$

Therefore,

$\rho V g = \rho_{w} V_{2} g\\\\\rho V = \rho_{w} V_{2}\\\\ \rho V = 1000 \times 0.85V\\\\\rho = 1000 \times 0.85\\\\\rho = 850$

Thus density of wooden block is 850 kilogram per cubic meter