Planet X moves in a nearly circular orbit of radius around a star

PHYSICS · Subjective · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

Planet X moves in a nearly circular orbit of radius

1.5\times10^{11}\,\text{m}

around a star. Its orbital period is observed to be

200\,\text{days}

. Planet Y revolves around the same star in a circular orbit of radius

6.0\times10^{11}\,\text{m}

. (a) Calculate the orbital period of Planet Y in days. (b) By what factor is the length of a year on Planet Y greater than that on Planet X?