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gourish

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## Homework Statement

There are two cubes of mass m. They are initially tied by a string tightly. They are kept from joining into each other because of a spring (which in this tied up state has a compression of ε) of coefficient of stiffness k. Find the minimum value of the quantity εk/mg so that when the string is cut and the spring is let loose to act, the lower cube jumps off the ground

## Homework Equations

consider the natural length as "l" of the spring and the center of mass of lower cube as the reference line

total mechanical energy (initial)=1/2 k ε^2+mg (l-ε)

total mechanical energy (after)=1/2kx^2+mg(l-x)

## The Attempt at a Solution

i found that k(e+x)/mg=2 but i did not get to the quantity to become εk/mg and did not understand how to relate the equations to the condition "the lower cube jumps off the ground" can anybody please help me