# How should I break down a tension force for free body diagrams?

Not a homework question instead its a doubt in concepts about vectors related to tension force

I was learning about vectors and i encountered a problem in breaking vector of tension force t, as I have given all details already please refer to it,

I am sorry to write question in image, but it my best possible handwriting , please dont discard it🙂

To explain my issue a little: In lower two diagrams I have drawn vector t in string t Which is pulling from both sides. But when I breaks vector t in separate cases, I gets vectors also in opposite direction(img 2 and img 3) Since single force cant have vectors in all four direction[two in 1 case and 2 in other] I concluded one of my fig 2 or 3 is wrong. Which is wrong as per you? Why do you the option you which you did not chose is wrong?

Also if you can theoritically or by intution explain how tension is pulling at both ends I would be grateful tp you.

• Depends on the perspective. If you want to draw the FBD of the ball, we see the force that’s acting on it only, not the force that is produced by it, so we take left one. But if we have to discuss about the force on the point of attachment, we take the right one. May 6 at 4:00

## 1 Answer

Your 2 drawings have identified the Newton's Third Law reaction pair. Suppose the tension drawn in your left drawing is $$\bf \vec T$$, then that on your right drawing is its equal and opposite pair, that is, $$-{\bf \vec T}$$.

Note that these forces act on different objects. The force in your left drawing is pulling on the ball, whereas the force in your right drawing is pulling on the ceiling. But you don't care about what's pulling on the ceiling, you only care about the forces acting on the ball, since you want to draw the Free Body diagram of the ball. Thus, your left diagram is the one you want.

• Welcome to Physics Stack Exchange! Please use the comments only to ask other useful information related to answer or some clarification, not for asking upvotes. May 6 at 3:56
• I am sorry now ,its fine May 6 at 4:13