A block of mass 5.0 kg is suspended from the end of a vertical spring which is stretched by 10 cm under the load of te block. The block is givena sharp impulse from below so that it acquires an upward speed of 2.0 m/s. How high will it rise? Take `g=10 m/s^2`

Answer

B, C

Explanation

`m=5kg, x=10cm=0.1m`
`v=2m/sec, h=?, g=10m/sec^2`
So, `k=(mg)/x`
`=50/0.1=500 N/m`

Total energy just after the blow
`E=1/2mv^2+1/2 kx^2`………..i
`Total energy at a height h
Total energy at a height h
`=1/2k(h-x)^2-mgh`
On solving we can get
`h=0.2m`
`=20cm`