Question

Calculate the force of gravity on the 0.60-kg mass if it were 1.3×107m above Earth's surface (that is, if it were three Earth radii from Earth's center).

Answer 1

The force of gravity between two objects is given by:

`F=G (m_1 m_2)/(r^2)`
where
G is the gravitational constant
m1 and m2 are the masses of the two objects
r is their separation

In this problem, the mass of the object is
`m_1=0.60 kg`, while the Earth's mass is
`m_2=5.97 \cdot 10^(24) kg`. Their separation is
`r=1.3 \cdot 10^7 m`, therefore the gravitational force exerted on the object is

`F=(6.67 \cdot 10^(-11)m^3 kg^(-1) s^(-2)) ((0.60 kg)(5.97 \cdot 10^(24) kg))/((1.3 \cdot 10^7 m)^2)=1.4 N`