A crate is pushed horizontally with 100 N across a 5 m floor. If the frictional force between the crate and the floor is 40 N, then the kinetic energy gained by the crate is

Options

A. 200 J
B. 240 J
C. 250 J
D. 300 J

Answer

D

Explanation

We know that,
`F - f = ma`
So, `100- 40 = ma`
`a= (600)/(m)`
Also, `v = sqrt( 2 as)`
Kinetic energy gained by the crate
`KE = (1)/(2) mv^(2)`
`KE = (1)/(2) m(2as)`
`KE = (1)/(2) xx m xx (2 x (60)/(m) xx 5)" "(because s = 5m)`
`KE = 300 J`