. A bullet moving with a velocity of 200 cm / s penetrates a wooden block and comes to rest after traversing 4 cm inside it. What velocity is needed for travelling distance of 9cm in same block

Options

A. 100 cm/s
B. 136.2 cm/s
C. 300 cm/s
D. 250 cm/s

Answer

C

Explanation

`v^2 = u^2 - 2as rArr u^2 = 2as `
`rArr u^2 prop s rArr (u^2)/(u_1) = (s_2/s_1)^(1//2)`
`rArr u_2 = (9/4)^(1//2) u_1 = 3/2 u_1 = 300cm/s`