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=(-0.1x)N` during its travel from x=20 m to x=30 m. Its final kinetic energy will be

Options

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

Answer

A

Explanation

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