Question

If the mass of earth is $80times$ of that of a planet and diameter is double that of planet and ${}^{\prime }{g}^{\prime }$ on the earth is $9.8m{s}^{-2}$, then the value of ${}^{\prime }{g}^{\prime }$ on the planet is =_____ $m{s}^{-2}$

• A. $4.9$
• B. $0.98$
• C. $0.49$
• D. $49$

Answer 1

Answer: (C)

$0.49$

$g=\frac{GM}{R^2}$

$g_p=g_e(\frac{M_p}{M_e})(\frac{R_e}{R_p}{)}^2=9.8(\frac{1}{80})(2{)}^2$

$g_p=9.8/20=0.49m/s^2$