A block of mass 20 kg is moving in x-direction with a constant speed of `10 ms^(-1)`. It is subjected to a retarding force `F=(-0.1 x)N` during its travel from `x=20 m` to `x=30m`. Its final kinetic energy will be

Options

A. 975 J
B. 450 J
C. 275 J
D. 250 J

Answer

A

Explanation

Applying work-energy therorem we get, `K_(f)-K_(i)=W`
`:. K_(f)=K_(i)+W`
`=1/2 xx20xx(10)^(2)+int_(20)^(30) (-0.1 x) dx`
`=1000 -0.1/2 (x^(2))_(20)^(30)=1000-25=975 J`