Question

The gravitational potential due to earth at infinite distance from it is zero. Let the gravitational potential at a point $P$ be $-5\, J\, kg ^{-1}$. Suppose, we arbitrarily assume the gravitational potential at infinity to be $+10\, J\, kg ^{-1}$, then the gravitational potential at $P$ will be

• A. $-5\, J\, kg ^{-1}$
• B. $+5\,J\, kg ^{-1}$
• C. $-15\, J\, kg ^{-1}$
• D. $+15\, J\, kg ^{-1}$

Answer 1

Answer: (B)

According to the problem, as the potential at $\infty$ increases by $+10\, J\, kg ^{-1}$, hence potential will increase by the same amount everywhere (potential gradient will remain constant).
Hence, potential at point $P=10-5=+5\, J\, kg ^{-1}$