Question

What is the force of gravity on a body of mass 150 kg lying on the surface of the earth? (Mass of earth = 6 x 10²⁴ kg; Radius of earth = 6.4 x 10⁶ m; G = 6.7 x 10^-11 Nm²/kg²)

Answer 1

F (gravitational force) = ?
G (gravitational constant) = 6.7 × 10⁻¹¹ Nm² kg⁻²
M (mass of earth)= 6 × 10²⁴  kg
m (mass of body) = 150 kg
r (radius of earth) = 6.4 × 10⁶ m
`F = (GMm)/r^2`
= `(6.7 xx 10^-11 xx 6 xx 10^24 xx 150)/(6.4 xx 10^6)^2`
= `(6.7 xx 10^-11 xx 6 xx 10^24 xx 150)/(6.4 xx 6.4 xx 10^12)`               (`10^(24-11) = 10^13`)
= `(6.7 xx 6 xx 15 xx 10^14)/(6.4 xx 6.4 xx 10^12)`   (`10^(14-12)=10^2`)
= `14.72 xx 10^2`
= 1472 N
Answer : Force of gravity = 1,472 N