Two identical blocks, each of mass m, are connected through a massless spring of force constant k and arranged as shown in fig the spring is compressed by an amount y by applying an external force and released
(a) What is the velocity of upper block when the spring is relaxed
(b) What should be the initial compression of the spring so that the lower block is just raised above the floor ?

Answer

`v=y(k/m-(2g)/y)^(1//2)and y' = (3mg)/k`

Explanation

(a) By conservation of `ME, 1/2 mv^(2)+mgy=1/2ky^(2)`
`(b) F gt 2mg(m_(1)=m_(2)),`
so, `F_("net")gt2mg+mg or=ky' = 3mg`