Q. The gravitational potential difference between the surface of a planet and a point 20 m above it is $14\ Jkg^{- 1}$. The work done in moving a 2.0 kg mass by 8.0 m on a slop of $60{^\circ}$ from the horizontal is equal to
A) 7 J
B) 9.6 J
C) 16 J
D) 32 J
Explanation
(b) Gravitational intensity,
$I = \frac{dV}{dx} = \frac{14}{20} = 0.7\ Nkg^{- 1}$
Acceleration due to gravity,
$g = I = 0.7\ Nkg^{- 1}$
Work done under this field in displacing a body on a slope of $60{^\circ}$ through a distance $s$
$= m(g\sin{60{^\circ}})s$
$= 2 \times \left( 0.7 \times \sqrt{3}/2 \right) \times 8 = 9.6\ J$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.