Question

An object displaces water of volume 0.2 $m^3$ when placed in a beaker of water. The density of water is 1‎000 $kg{m}^{-3}$. What is the magnitude of the buoyant force acting on the object? Take g = $10m{s}^{-2}$

• A.
  5 kN
• B.
  2 kN
• C.
  3 kN
• D.
  2.45 kN

Answer 1

The correct option is B

2 kN
According to the Archimedes' principle, the buoyant force acting on an object when it is fully or partially submerged is equal to the weight of the liquid displaced by the object.

Here, volume of the water displaced (V) = $0.2m^3$

mass of the water displaced (m)
= volume $\times$ density of the water
= $0.2m^3\times 1000kg{m}^{-3}$
= 200 kg

Weight of the water displaced = mg
= $200kg\times 10m{s}^{-2}$
= 2000 N = 2 kN

Thus, the buoyant force acting on the object is 2 kN.