Physics Force of Gravity

Question

Calculate the force of gravity on the 1.5-kgkg mass if it were 6.4×10⁶ mm above Earth's surface (that is, if it were two Earth radii from Earth's center)

Answer 1

This question requires use of Newton's Universal Law of Gravitation.

where G = 6.67×10⁻¹¹ N⋅m²/kg², M = mass of Earth (5.97×10²⁴ kg), m = 1.5 kg, and r = 2 x 6.4×10⁶ m (or 1.28×10⁷ m).

Plug and chug carefully into your calculator, and you should arrive at the answer of 3.65 N.

Note that means that gravity only has a strength of 2.43 N/kg (which is, not coincidentally, really close to 1/4 of 9.8 N/kg! (Keep in mind that the numbers we are using are "rounded off"...hence it not being "exact.")

Due to the inverse square relationship between gravitational force and orbital radius, when r x 2, g x 1/4!!

Hope this helps!