A small block of mass m is placed on a bigger block of mass M which is placed on a horizontal frictionless plane.
The two blocks are given equal speeds u but in opposite directions as shown in the figure. After sometime, it is
observed that both the blocks are moving in the direction of motion of the lower block, with a velocity greater
than $\frac{u}{2} .$ It can be concluded that

M > 3m

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3M < m

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M > mm

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M. m can have any value such that M > m.

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Solution

The correct option is A M > 3m
Total momentum is con $(M + m) \frac{u}{2} < (M - m) u$
or $M > 3 m .$ served along the horizontal direction and so

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