Question

If the water displaced by an object has a volume of 0.1 m3, what is the buoyant force exerted
on that object?

Answer 1

Answer:

Approximately $1000 \; {\rm N}$ (assuming that $g = 10\; {\rm N \cdot kg^{-1}}$.)

Explanation:

The buoyant force on an object is equal to the weight of the liquid that this object has displaced.

In this example, the object displaced $V = 0.1\; {\rm m^{3}}$ of water. The density of water is $\rho = 1.00 \times 10^{3}\; {\rm kg \cdot m^{-3}}$. Thus, the mass of the water displaced would be $m = \rho\, V = 1.00 \times 10^{2}\; {\rm kg}$.

Since $g = 10\; {\rm N \cdot kg^{-1}}$ by assumption, the weight of that $m = 1.00 \times 10^{2}\; {\rm kg}$ of water would be $m\, g = 1.00 \times 10^{3}\; {\rm N}$. Hence, the buoyant force on this object would be $1.00 \times 10^{3}\; {\rm N}$, which is $1000\; {\rm N}$ when rounded to one significant figure (as in volume.)