Consider two masses connected by a string over a pulley, like so:
Where mass $M$ is held in place by a hand.
I'm asked to draw free-body diagrams for mass $m$ and $M$ individually, and identify third-law pairs in the two diagrams. I'm then asked to consider when the hand moves and mass $m$ begins accelerating downwards.
We can assume the surface to be frictionless and the pulley to be massless.
It doesn't seem to me that there are any third-law pairs. The only third-law pairs I can identify in the diagram are the normal forces between the hand and the block (in the first case).
Am I thinking about this wrong?