Does Torque act on a disc rotating with constant angular velocity

In summary: 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?isn't the torque 0 on circular bodies rotating with constant angular velocity?
  • #1
crazycyrus
3
0
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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  • #2
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.
 
  • #3
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?
 
  • #4
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.
 
  • #5
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?
 

FAQ: Does Torque act on a disc rotating with constant angular velocity

Does a disc rotating with constant angular velocity experience torque?

Yes, a disc rotating with constant angular velocity does experience torque. This is because torque is defined as the measure of the force that causes an object to rotate around an axis. Even if the angular velocity remains constant, there is still a force acting on the disc to maintain its rotation, and this force is known as torque.

What factors affect the amount of torque acting on a rotating disc?

The amount of torque acting on a rotating disc depends on several factors, including the magnitude of the force applied, the distance from the axis of rotation where the force is applied, and the angle between the force and the axis of rotation. These factors can be represented by the equation: τ = r x F x sin(θ), where τ is torque, r is the distance, F is the force, and θ is the angle.

Can torque act on a disc even if there is no external force?

Yes, torque can still act on a disc even if there is no external force. This is because torque can also be created by internal forces, such as the force of friction between the disc and its axis of rotation. In this case, the torque would cause the disc to slow down and eventually stop rotating.

How does the direction of torque affect the rotation of a disc?

The direction of torque plays a crucial role in determining the direction of rotation of a disc. According to the right-hand rule, if the direction of torque is into the page, the disc will rotate counterclockwise, and if the direction of torque is out of the page, the disc will rotate clockwise. This rule applies in most cases, but there are some exceptions, such as when the disc is rotating in a non-uniform manner.

Can torque act on a disc without causing it to rotate?

No, torque cannot act on a disc without causing it to rotate. This is because torque is the rotational equivalent of force and is always responsible for causing or changing the rotation of an object. If the torque acting on a disc is not enough to overcome its inertia, the disc may not rotate, but there will still be an equal and opposite torque acting on the disc.

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