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A bullet of mass m hits a block of mass M elastically. The transfer of energy is the maximum, when :

Asked in NEET 2023 Manipur · Energy transfer in elastic collisions

Answer: (1) M=m

Step-by-step solution

Idea: in a head-on elastic collision with a target at rest, the fraction of the projectile's kinetic energy handed over is (4mM)/((m+M)²).

Write M=km: the fraction becomes (4k)/((1+k)²).

That expression is 1 at k=1 and falls away on either side, since (1+k)²-4k=(1-k)²≥0.

So the transfer is complete only when k=1.

M=m: the bullet stops dead and the block moves off with the whole of the energy.

Why the other options are wrong

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