A block of mass 5 kg is resting on a smooth surface at what angle a force of 20 N be acted on the body so that it will acquire a kinetic energy of 40 J after moving 4 m?

Options

A. `30^@`
B. `45^@`
C. `60^@`
D. `120^@`

Answer

C

Explanation

According to work energy theorem,
`W = DeltaKE`
`implies FS cos theta =1/2 mv^2 -1/2 "mu"^2`
`implies 20 xx 4 xx cos theta = 40 implies cos theta =1/2`
`implies cos theta = cos 60^@ implies theta = 60^@`