Bruce Willis tethered to the asteroid sees the Earth closing

Bruce Willis, tethered to the asteroid, sees the Earth closing in on him at the same relative speed. If the mass of the Earth is approximately 6 x 1024 kg, show that his estimate of its kinetic energy is 1.2 x 1033 J.

Solution

Given : M = 6*10²⁴ kg

Earth relative speed = v = 20km/s = 20*1000 m/s

So,

Kinetic energy = 0.5*m*v² = 0.5*6*10²⁴*20000²= 1.2*10³³ J