A body of mass 2 kg thrown vertically from the ground with a velocity of `8 ms^(-1)` reaches a maximum height of 3m. The work done by the air resistance is (acceleration due to gravity `=10 ms^(-2)`)

Options

A. 4J
B. 60J
C. 64J
D. 8J

Answer

A

Explanation

Initial energy of particle
`=(1)/(2) mv^(2)=(1)/(2)xx2xx8^(2)=64 J`
Final energy of particle at maximum height
`=mgh =2xx10xx3=60 J`
work done against air friction
=Loss of energy =64-60=4 J