A particle of mass starts from rest at infinity and falls directly towards Earth

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

Problem

A particle of mass

1\,\text{kg}

starts from rest at infinity and falls directly towards Earth. Calculate its speed when it is

500\,\text{km}

above Earth’s surface. Take

G = 6.67\times10^{-11}\,\text{N m}^2\text{kg}^{-2}

M_{E}=6.0\times10^{24}\,\text{kg}

and

R_{E}=6.4\times10^{6}\,\text{m}