Use Newton’s Law of Gravity to calculate the force of gravity between a 39 kg person and Earth.

Answer 1

F = M g, where g = 9.8 m/s^2,
or, if you really must use that Newton law,

F =G*Me*M/Re^2

M = 39 kg
G = universal gravity constant
Re = Earth radius
Me = Earth mass

You will have to look up the last three quantities. I have not memorized them.

The answers should agree

Answer 2

Consider a pulse of laser light aimed at the moon that bounces back to earth. The distance between Earth and Moon is 3.8 x 10 (small eight above ) m. Show that the round-trip time for the light is 2.5 s.