Confusion about tension and pulleys

[hgfhh123]

Homework Statement

I am a little confused about the concept of tension as it relates to pulleys. I am studying torque right now, and it says in the textbook that the tension in the rope around a pulley produces a torque that causes the pulley to turn. I don't fully understand this. I thought that tension was a pair of opposing forces that acted throughout the rope at each point in the rope. However, I don't understand how the same force would cause the pulley to turn. Since there is no friction between the rope and pulley, I don't understand why the pulley would turn in the first place.

Homework Equations

The Attempt at a Solution

 

[ehild]

Homework Statement

I am a little confused about the concept of tension as it relates to pulleys. I am studying torque right now, and it says in the textbook that the tension in the rope around a pulley produces a torque that causes the pulley to turn. I don't fully understand this. I thought that tension was a pair of opposing forces that acted throughout the rope at each point in the rope. However, I don't understand how the same force would cause the pulley to turn. Since there is no friction between the rope and pulley, I don't understand why the pulley would turn in the first place.

Homework Equations

The Attempt at a Solution

There is static friction between the rope and pulley. That makes the pulley move together with the rope. The two pieces of the rope exert torques RT_a and RT_b on the pulley at points A and B. (R is the radius of the pulley). If the pulley is massless zero torque is enough to rotate it with a certain angular acceleration, so the tension is the same in both pieces of the rope. If the pulley has got I moment of inertia, the tensions Ta and Tb must be different to rotate the pulley with angular acceleration α: α=R(Tb-Ta)/I.


ehild

 

[bapul4u]

Its the frictional force between the string and pulley that cause the pulley to rotate when the string moves..