Question

I friend who argues that Tension is a compressive force, but I think that Tension is a stretching force. He gives examples that are somewhat valid, but I still stick with what I think. For example, in a problem where a rope is tied to two trees - one end is tied to one tree and the other on the other tree, my friend thinks that the tension will point away from the bark, but I think the opposite. Who wins and why? Thanks in advance! :)

Answer 1

It is relative to your choice. If you wish the x-axis to be increasing in the downwards direction, then it is so. If you wish it to be the other way around, then it is how you wish. Just follow the Right-Handed coordinate system.

Answer 2

I don't think I understand what you mean. Yes, the force diagram depends on your axes and what you wish to call +x, -y, etc. But the actual physical interpretation shouldn't depend on that.

Answer 3

Tension by a rope/string is a 'pulling' force, whereas a spring or a rod can also push. A rod can even exert a sideways action.

A rope or an extended spring will always exert forces on each end directed inwards.
Force in A is to the right. Force in B is to the left.
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