# T1=T2 how do i motivate?

#### Optikspik

1. The problem statement, all variables and given/known data

How do i motivate that T1 = T2 in this system.

without just saying "Oh" its the same rope, like more in depth "why"

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#### SteamKing

Staff Emeritus
Homework Helper
What do you mean by 'motivate'?

#### Optikspik

The question is why can we say that t1 = t2 in this problem? Why? What is the reason?:

#### lep11

The question is why can we say that t1 = t2 in this problem? Why? What is the reason?:
By assuming that the rope is massless.

#### Optikspik

Why is t1=t2? Has it something to do with newtons third law, u guys dont explain very well sorry..

#### SteamKing

Staff Emeritus
Homework Helper
Why is t1=t2? Has it something to do with newtons third law, u guys dont explain very well sorry..
Well, your diagram is open to some interpretation. Is it a static figure? Is there friction present for the surface on which M rests? Are D and M supposed to have the same mass?

If you draw a free body diagram which isolates the sheave, you should be able to determine how T1 relates to T2, assuming of course, you can answer the questions posed above.

#### Optikspik

.. This dosent help me, just think of a normal pulley problem where T1 is equal to T2, but why? They are equal, but is it because its "one string" or because of "newtons third law" or why? like common, this is a very easy question, but its quite hard if ur teacher havent told you (in this case told me)

#### SteamKing

Staff Emeritus
Homework Helper
.. This dosent help me, just think of a normal pulley problem where T1 is equal to T2, but why? They are equal, but is it because its "one string" or because of "newtons third law" or why? like common, this is a very easy question, but its quite hard if ur teacher havent told you (in this case told me)
Well, the easy answer is it's the same rope. When you pull on one end with a certain amount of force, that same force is transmitted all the way back to the point where the other end of the rope is attached. That's the First Law of Ropes.

#### Optikspik

Thanks :)

"T1=T2 how do i motivate?"

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