(a). A cube of side 5 cm is immersed in water and then in saturated salt solution. In which case will it experience a greater buoyant force. If each side of the cube is reduced to 4 cm and then immersed in water, what will be the effect on the buoyant force experienced by the cube as compared to the first case for water. Given reason for each case.
(b). A ball weghing 4 kg of density 4000 `kg//m^(3)` is completely immersed in water of density `10^(3)kg//m^(3)` find the force of buoyancy on it. (given `g=10m//s^(2))`

Explanation

(i) Buoyant force, F=V `rho`g
(where, `rho` = Density of water, V = Volume of water displaced by body)
Buoyant force depends upon volume. So, in saturated solution, cube will experience a greater buoyant force.
If each side of the cube is reduced to 4 cm, then the volome of cube become less. As buoyant force is directly proportional to the volume. So, buoyant force will be less than as compared to the first case for water.
(ii) The magnitude of the buoyant force given by F = V `rho` g
whre V = Volume of body immersed in water or volume of water displaced, `rho` = Density of liquid. `" "[because"Given, mass of a ball = 4 kg, density = 4000 kgm"^(-3)]
`:." ""Volume of `"solid"=("Mass")/("Density")`
`" "=(4)/(4000)=(1)/(1000)m^(3)`
`"Buoyancy"," "F=V"rhog`
`" "=(1)/(1000)xx1000xx10=10N`