The contact force is equal to 36N. (Option 4)
Why?
Since there is no information about the direction of the force, I'll assume that the force is horizontal, acting from left to right, and the and the blocks are next to the other.
Calculations:
Let be the block "M" be on the left, and "m" be on the right,
So,
For the block "m", we have:
For the block "M", we have:
Substituting "a" from the first equation, we have:
Hence, we have that the contact force is equal to 36N.
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