A spring gun has a spring constant of `80Ncm^(-1)`. The spring is compressed `12cm` by a ball of mass `15g`. How much is the potential energy of the spring ? If the trigger is pulled, what will be the velocity of ball ?

Explanation

Here, `K=80Ncm^(-1)=80xx100Nm^(-1)`
`x=12cm=12xx10^(-2)m,`
`m=15g=15xx10^(-3)kg`
`P.E` of spring `=(1)/(2)Kx^(2)`
`=(1)/(2)xx80xx100(12xx10^(-2))^(2)=57.6J`
Again, KE of ball `= P.E.` of spring
`(1)/(2)m upsilon^(2)=57.6, upsilon=sqrt((2xx57.6)/(15xx10^(-3)))=sqrt(7680)`
`-87.6m//s`