Question

A person brings a mass of $1kg$ from infinity to a point A. Initially the mass was at rest but it moves with a speed of $2m/s$ as it reaches A. The work done by the person on the mass is $3J.$ The potential of A is.

• A. $3J/kg$
• B. $2J/kg$
• C. $5J/kg$
• D. $7J/kg$

Answer 1

Answer: (C)

$5J/kg$

$\text{Initially the total energy of the mass is zero.}$

$\text{Finally the kinetic energy of mass}=\frac{1}{2}m{v}^2=2\text{J}$

$\text{Work done on the mass}=3\text{J}$

$\text{Therefore the potential energy of mass at point A}=5\text{J}$

$\text{Therefore the potential at point A is}5\text{J/kg}$