Planet X has a gravitational field strength of at its surface

PHYSICS · Single correct · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

Planet X has a gravitational field strength of

18Nkg^{-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)

6ms^{-2}

(B)

18ms^{-2}

(C)

54ms^{-2}

(D)

162ms^{-2}