A body of mass 100 kg falls on the Earth from infinity. What will be its velocity on reaching the Earth? What will be its K.E. ? Radius of the Earth is 6400 km and `g=9.8ms^(-2)`

Explanation

A body thrown up with escape velocity `v_(e)` reaches infinity. Hence a body falling on the Earth from infinity should come back with velocity `V_(e)` given by
`v_(e)=sqrt(2gR_e)=sqrt(2xx9.8xx6400xx10^(3))`
`=11.2xx10^(3)ms^(-1)=11.2kms^(-1)`
`K.E=(1)/(2)mv_(e)^(2)=(1)/(2)xx100xx(11.2xx10^(3))^(2)`
`=6.27xx10^(9)J`