Question

A person brings a mass $2 \,kg$ from $A$ to $B$. The increase in kinetic energy of mass is $4J$ and work done by the person on the mass is $-10J$. The potential difference between $B$ and $A$ is .......J / kg

• A. 4
• B. 7
• C. -3
• D. -7

Answer 1

Answer: (D)

The potential energy is given as,
$
\left( U _{ B }- U _{ A }\right)+\left( K _{ B }- K _{ A }\right)= W _{ AB }
$
$
\left( U _{ B }- U _{ A }\right)+4=-10
$
$
\left( U _{ B }- U _{ A }\right)=-14 J
$
The potential difference is given as,
$
\begin{array}{l}
\left( V _{ B }- V _{ A }\right)=\frac{\left( U _{ B }- U _{ A }\right)}{ m } \\
\left( V _{ B }- V _{ A }\right)=\frac{(-14)}{2} \\
\left( V _{ B }- V _{ A }\right)=-7 J / kg
\end{array}
$
Thus, the gravitational potential difference between $B$ and $A$ is $-7 J / kg$.