Question

A cubical vessel of height $1\,m$ is full of water. What is the amount of work done in pumping water out of the vessel? (Take $g = 10\, m s^{-2}$)

• A. $1250\, J$
• B. $5000\, J$
• C. $1000\, J$
• D. $2500\, J$

Answer 1

Answer: (B)

The volume of water contained in the vessel would be equal to $V=l^{3}=1^{3} m ^{3}=1 \,m ^{3}$. Assuming water to be pure so the density of water would be equal to $d=1000 \,kg / m ^{3}$, hence the mass of water contained in the vessel would be equal to $m=V d=1000 \,kg$. Thus, the work done would be equal to
$W=m g h=1000 \times 10 \times \frac{1}{2}=5000 \,J$