Does Torque act on a disc rotating with constant angular velocity

AI Thread Summary
A disc rotating with constant angular velocity has no angular acceleration, which implies that the net torque acting on it is zero. However, in practical applications like turbines, torque is still relevant because it accounts for the balance of forces, including resistive torques from friction and other loads. The power produced by a turbine is calculated using the equation Power = Torque × Angular Velocity, indicating that while net torque is zero, there are equal and opposite torques at play. In ideal conditions, such as a perfect vacuum with no losses, the torque could be considered zero, but this is not realistic in real-world scenarios. Therefore, torque is essential for understanding power generation in systems like turbines, even when they operate at constant angular velocity.
crazycyrus
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Hey Folks
I have rather a silly doubt i guess...
It goes like this

Consider a disc rotating about a fixed axis with constant angular velocity. Which means it has no angular acceleration ie it must be 0. Now since Torque=(moment of inertia)*(angular acceleration). hence the torque acting on the disc must be zero.
But i have come across situations where torque comes into the picture while calculating the power produced by say a Turbine(rotating with a constant angular velocity) . where Power=(torque)*(angular velocity)...?? Why is it so? isn't the torque 0 on circular bodies rotating with constant angular velocity?
 
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The torque in a real system will never be 0, especially in a turbine engine. The aerodynamic loads alone load the rotating components highly. The only time you would have the torque = 0 is in a perfect vacuum with no losses due to things like friction and windage.
 
Ok under those conditions(vaccum,no friction losses etc) will it be appopriate to say the power produced by a turbine rotating at constant angular velocity is 0 since torque is 0?
 
crazycyrus said:
isn't the torque 0 on circular bodies rotating with constant angular velocity?
If the angular velocity is constant, then the net torque is zero. But as FredGarvin says, you may need to apply a torque to overcome friction, etc.
 
If the angular acceleration of the disk is zero that means the net torque is zero.

In the case of a turbine rotating at constant angular velocity, you have equal and opposite torques acting on both sides of the central shaft. The first torque is the output torque produced by the turbine engine, and the second torque is the resistive torque of the prime mover (which might be a generator). Since they are equal and opposite, the turbine rotates at constant angular velocity.

The power equation you gave is correct.


crazycyrus said:
Hey Folks
I have rather a silly doubt i guess...
It goes like this

Consider a disc rotating about a fixed axis with constant angular velocity. Which means it has no angular acceleration ie it must be 0. Now since Torque=(moment of inertia)*(angular acceleration). hence the torque acting on the disc must be zero.
But i have come across situations where torque comes into the picture while calculating the power produced by say a Turbine(rotating with a constant angular velocity) . where Power=(torque)*(angular velocity)...?? Why is it so? isn't the torque 0 on circular bodies rotating with constant angular velocity?
 
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