A bolck of mass `10 kg` is moving in x-direction with a constant speed of `10 m//s`. it is subjected to a retardeng force `F=-0.1 x J//m`. During its travel from `x =20m` to `x =30 m`. Its final kinetic energy will be .

Options

A. `475 J`
B. `450 J`
C. `275 J`
D. `250 J`

Answer

A

Explanation

`K_(f)-K_(i) =W =int Fdx`
`:. K_(f) =K_(i) + int_(20)^(30)(-0.1x)dx`
`1/2 xx 10 xx (10)^(2)-[0.1(x^(2))/(2)]_(20)^(30)`
`475 J`.