A bullet of mass 0.02 kg travelling horizontally with velocity 250`ms^(-1)` strikes a block of wood of mass 0.23 kg which rests on a rough horizontal surface. After the impact, the block and bullet move together and come to rest after travelling a distance of 40m. The coefficient of sliding friction of the rough surface is `( g = 9.8 ms^(_2))`

Options

A. `0.75`
B. `0.61`
C. `0.51`
D. `0.30`

Answer

C

Explanation

`m_1u_1 = (m_1+m_2) v`
`implies v = ((0.02)/(0.02+0.03))xx250`
`implies v=2/50 xx250 = 20m//s`
Conservation of energy `1/2 mv^2 = mu N xxS`
`implies 1/2 xx0.25 xx400 = mu xx 0.25 xx9.8 xx40`
`implies mu = 5/(9.8) = 0.51`