Question

Calculate the force of gravity on the 1-kg mass if it were 1.3×10⁷ m above Earth's surface (that is, if it were three Earth radii from Earth's center).

Express your answer to two significant figures and include the appropriate units.

Answer 1

Apply universal gravitational law

F = G M_E m/r^2

= G M_E m/r^2

  = G M_E m/r^2

= 6.67* 10^-11 (5.98* 10^24)1/(6371000+1.3* 10^7)^2

=1.06 N

= 1.1 N ( rounding two significant)