Two blocks of masses $$2$$ kg an $$4$$ kg are connected to the free ends of a spring of force constant $$800N/m$$. The blocks are pulled apart so that the spring is stretched by a length ‘x’m. and are released simultaneously, When the spring acquires its natural length, velocity of $$2$$ kg block is $$4m/s$$. Then ϕ elastic potential energy stored in the spring just after the blocks are released is (the$$ surface is $$smooth)

Question

Two blocks of masses $$2$$ kg an $$4$$ kg are connected to the free ends of a spring of force constant $$800N/m$$. The blocks are pulled apart so that the spring is stretched by a length ‘x’m. and are released simultaneously, When the spring acquires its natural length, velocity of $$2$$ kg block is $$4m/s$$. Then ϕ elastic potential energy stored in the spring just after the blocks are released is (the$$ surface is $$smooth)

Infinity Learn · Accepted Answer

Conserving linear momentum,  $$4$$×$$v=2$$×$$4$$ ⇒$$v=2m/s$$    Elastic potential energy stored in the springTotal kinetic energy of the blocks $$=12$$×$$2$$×$$42$$×$$12$$×$$4$$×$$22J=24J$$

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