A block of mass `5 kg` is released from rest when compression in spring is `2m`. Block is not attached with spring and natural length of the spring in `4m`. Maximum height of block from ground is `:(g=10m//s^(2))`

Options

A. 5.5 m
B. 4.5 m
C. 6 m
D. 7.5 m

Answer

A

Explanation

By energy conservation,
`(1)/(2) kx^(2) = mgh + (1)/(2) mv^(2)`
`=(1)/(2)xx300xx(B)^(2)=5 xx10xx2+(1)/(2)xx5v^(2)`
`rArr v^(2)=200`
Also, `H=(v^(2)sin^(2)30^(@))/(2g)=2.5 m`
So, total height from ground
`= 2+ 2.5 = 5.5 m`.