A block of mass `2kg` is attached with a spring of spring constant `4000Nm^-1` and the system is kept on smooth horizontal table. The other end of the spring is attached with a wall. Initially spring is stretched by `5cm` from its natural position and the block is at rest. Now suddenly an impulse of `4kg-ms^-1` is given to the block towards the wall.
Approximate distance travelled by the block when it comes to rest for a second time (not including the initial one) will be (Take `sqrt(45)=6.70`)

Options

A. (a) `30cm`
B. (b) `25cm`
C. (c) `40cm`
D. (d) `20cm`

Answer

B

Explanation

Again using,
`E_i=E_f`
`:. 1/2xx2xx(2)^2+1/2xx4000xx(0.05)^2`
`=1/2xx4000xxx^2`
`:. x=0.067m=6.7m`=compression
`:. d=5cm+6.7cm+6.7cm+6.7cm`
`~~25cm`