Altitude where Earth’s gravitational field weakens

PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

Altitude where Earth’s gravitational field weakens (i) The acceleration due to gravity at Earth’s surface is

g = 9.8\,\text{m\,s}^{-2}

and Earth’s radius is

6.4\times10^{6}\,\text{m}

. At what altitude

h

above the surface does the gravitational field reduce to

0.25\,g

? Express

h

in kilometres. (ii) At this altitude, what is the weight of an astronaut of mass

70\,\text{kg}