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Suppose in extensible mass less rope is placed on a pulley surface, obviously there will be a normal force pairs between the Pulley and rope. right? Why do the the Normal force of rope on to pulley($N_{pulley,rope}$) is not considered while analyzing the free body diagram of Pulley? enter image description here

I am adding the picture where I was confused, Fig I shows the free body diagram of Pulley A.enter image description here

Link for the video:-

  • $\begingroup$ What are you solving for? $\endgroup$ – Danny LeBeau Jul 19 '20 at 7:52
  • $\begingroup$ I am trying to find out all the forces on the pulley. $\endgroup$ – Unknown x Jul 19 '20 at 7:57
  • $\begingroup$ Can I add the picture in my question, where I was confused? $\endgroup$ – Unknown x Jul 19 '20 at 7:58
  • $\begingroup$ Yes please do that. $\endgroup$ – Danny LeBeau Jul 19 '20 at 8:01
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    $\begingroup$ The pulley and rope are considered to be perfect. That is there is no friction between the contact points of the pulley and rope . The rope is massless so it cannot have any weight of its own . This might seem weird at first but thats how an introduction is given in NLM. Once the basic concept is understood , you will find problems where you have to consider the mass of the rope $\endgroup$ – Jdeep Jul 19 '20 at 8:21

He didn't considered normal force since the rope and pulley are massless . So there is no weight of rope (mg pulling the rope or the pulley).

In real life you are correct , there is a normal force between the rope and pulley.

  • $\begingroup$ But then, How he consider tension? Normal force is nothing to do with the weight. right? It is generated due to molecular level repultion. right? $\endgroup$ – Unknown x Jul 19 '20 at 8:14
  • $\begingroup$ Tension is not due to the rope's weight.It's due to that man pulling the rope. $\endgroup$ – Danny LeBeau Jul 19 '20 at 8:20
  • $\begingroup$ Thank you. Now,this lead me one more question. Why $T_1$ is directed upward in the figure 1? $\endgroup$ – Unknown x Jul 19 '20 at 8:37
  • $\begingroup$ Does the pulley has any role in generating tension? $\endgroup$ – Unknown x Jul 19 '20 at 8:37
  • $\begingroup$ I am confused with these questions. please help me. $\endgroup$ – Unknown x Jul 19 '20 at 8:38

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