It’s a stupid question but why doesn’t mg=T3+T1sintheta+T2sinBeta ?
Suppose I understand why T1 and T2 are not acting on the mass
Having gotten the diagram on the right I would’ve understood why T3=mg but our teacher gave us the diagram on the left. I understand why there are 2 T3’s in the string, if 2 ppl pull on a book, both will feel the forces, but This is confusing me when it comes to deciding what forces act on the mass If there’s a T3 force upwards in the string and another one downwards in the same string, don’t they cancel out the effects of each other ?
There's the mg downward force and the tension upward force acting on the mass. Since the mass is not moving, then it is in equilibrium and T3=mg. Nothing else is directly acting on the mass, therefore you ignore everything else in the diagram.