Physics

Problem

Planet X has a gravitational field strength of

18 \text{ N kg}^{-1}

at its surface. Planet Y has the same density as X but three times the radius of X. What is the gravitational field strength at the surface of Y? A.

6 \text{ m s}^{-2}

18 \text{ m s}^{-2}

54 \text{ m s}^{-2}

162 \text{ m s}^{-2}