A body of mass 5 kg is acted upon by a variable force.the force varies with the distance covered by the body. Find the kinetic energy of the body when the body has covered 30 m distance ? Assume that the body starts from rest.

Options

A. 295 J
B. 105J
C. 300 J
D. 80 J

Answer

A

Explanation

Work done by force when body has covered 25 m
=Area under curve upto distance 25 m
Now `W=DeltaK=1/2 xx5(v^(2)-0^(2))=250`
Area between 25 m to 30 m is (1/2)5x18=45
So total workd done by variable force,till 30 m is 250 +45=295 joule
So change in kinetic energy =295 J. So final kinetic energy =295 J