# Tension, real or fake

It is a very simple problem. a massless rope but with friction is climbed upon by a monkey. I need to understand the working of forces here.

Suppose the monkey is applying a force F on the rope. So it in return feels the reaction force F towards the ceiling. Tension also develops here in the rope as well due to the force F and it is equal to F.

Now we know that the rope will pull the monkey up with tension force. so the monkey feels F upwards. But the monkey at the beginning also experiencing force F from the 3rd law reaction. So is it that the monkey applying a force of F downward will feel a force 2F upwards in return.

Now bringing friction into the play. When the monkey pulls down the friction pulls up.Let the friction be f. now the rope also feels a force of f. It means that the final tension should increase and become F+f. So the monkey will now feel an upward tension of F+f.

So eventually we have a monkey applying a force of F on a rope and getting 2F+f force in return.(one F from 3rd law reaction when it applied a force F in the first place. Another F+f from the tension in the rope.

So where am I wrong here ?

• Do you know what free body diagrams are? You are double-counting F because you haven't drawn the free body diagram. There is a separate FBD for the rope and the monkey. – DKNguyen May 12 at 20:41
• yup I studied them but still I doubt regarding this that wether the tension is playing the part of the 3rd law reaction or not and other things in the question. – chittaranjan rout May 12 at 20:45
• You're like quintuple counting forces. – Jerry Schirmer May 12 at 20:45
• pls show me where I am wrong. I know I am terribly wrong – chittaranjan rout May 12 at 20:47
• Draw the FBD first. Then you won't have silly mistakes like thinking "Suppose the monkey is applying a force F on the rope. So it in return feels the reaction force F towards the ceiling. Tension also develops here in the rope as well due to the force F and it is equal to F. Now we know that the rope will pull the monkey up with tension force. so the monkey feels F upwards. But the monkey at the beginning also experiencing force F from the 3rd law reaction. So is it that the monkey applying a force of F downward will feel a force 2F upwards in return." are two different forces. – DKNguyen May 12 at 20:47