Q. If a planet consists of a satellite whose mass and radius were both half that of the earth, the acceleration due to gravity at its surface would be ($g$ on earth $= 9.8\ m/s{ec}^{2}$)

A) $4.9m/s{ec}^{2}$
B) $8.9m/s{ec}^{2}$
C) $19.6m/s{ec}^{2}$
D) $29.4m/s{ec}^{2}$
Explanation

(c) $g = \frac{GM}{R^{2}}\therefore g \propto \frac{M}{R^{2}}$
According to problem $M_{p} = \frac{M_{e}}{2}$ and $R_{p} = \frac{R_{e}}{2}$
$\therefore\frac{g_{p}}{g_{e}} = \left( \frac{M_{p}}{M_{e}} \right)\left( \frac{R_{e}}{R_{p}} \right)^{2} = \left( \frac{1}{2} \right) \times (2)^{2} = 2$
$\Rightarrow g_{p} = 2g_{e} = 2 \times 9.8 = 19.6\ m/s^{2}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

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