Question

A planet has mass 6.4into 10^6m. calculate energy required to remove on object of mass 800 kg from the surface of the planet to infinity
​

Answer 1

126.1 MJ/kg

Explanation:

Mass of planet = 6.4×10^24 kg

Radius = 3.4×10^6 m

G = 6.7*10^(-11) Nm^2/kg^2

The gravitational potential at surface is:

P = -(G*M)/r

= - [6.7*10^(-11) × 6.4×10^24 ]/3.4×10^6

= - 12.61 × 10^7

= -1.261 × 10^8 J/kg

P= -126.1 MJ/kg

Now if 10MJ/kg work is done to lift a particle to some height from surface the potential will be -116.1 MJ/kg .

So, the required work = 126.1 MJ/kg

[raised to a height where gravitational potential reaches zero . From 0 to infinity it can not be measured ]