A spherical asteroid has mass and radius

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

Problem

A spherical asteroid has mass

2.0\times10^{22}\,\text{kg}

and radius

6.4\times10^{5}\,\text{m}

. The universal gravitational constant is

6.67\times10^{-11}\,\text{N\,m}^2\!\text{/kg}^2

. A stone is released from rest at a height of

20\,\text{m}

above the asteroid’s surface. Approximately how long will it take to reach the surface? (Neglect any atmosphere.) (a)

2.0\,\text{s}

(b)

10\,\text{s}

(c)

3.5\,\text{s}

(d)

6.1\,\text{s}