Friction as B times angular speed?

In summary, The equation Tfriction = B×dθ/dt represents the moment caused by friction in a rotating motor, with B representing the viscous damping coefficient. This equation is analogous to the translation friction equation F = B dv/dt and is commonly used in control systems. The damping force in this equation is caused by a viscous fluid, such as oil, and is represented by a dashpot in diagrams.
  • #1
tamtam402
201
0
Friction as B times angular speed??!

Hi,

My control systems book uses a weird notation for the moment caused by friction in a rotating motor. The equation is

Tfriction = B×dθ/dt

Where does this equation come from? The author assumes the reader is already familiar with this equation.

The only definition of friction I am familiar with is F = μN. Obviously the torque is given by T = Fd. I have never learned about torques in rotational systems so I assume the equation used in the book is well known and analogous to the translation friction equation.

What exactly is the B coefficient called? Where does this equation come from?

Thanks.
 
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  • #2
That equation for translational motion would be F = B dv/dt. It is termed the damping force.

B is the viscous damping coeficient. A damper is represented as a pictogram of a dashpot where a viscous fluid such as oil provides the damping force as a linear function of translational velocity dv/dt, or in rotational motion dθ/dt.
 

FAQ: Friction as B times angular speed?

1. What is the equation for "Friction as B times angular speed"?

The equation for "Friction as B times angular speed" is F = Bω, where F is the frictional force, B is the coefficient of friction, and ω is the angular speed.

2. How is "Friction as B times angular speed" related to rotational motion?

"Friction as B times angular speed" is related to rotational motion as it represents the force that opposes the motion of an object that is rotating at a constant angular speed. This force is known as frictional torque and is caused by the coefficient of friction between the object and its surface.

3. What factors affect the value of "Friction as B times angular speed"?

The value of "Friction as B times angular speed" is affected by the coefficient of friction, which depends on the materials in contact and the roughness of their surfaces. It is also affected by the angular speed of the object, as a higher speed will generate a larger frictional force.

4. Can "Friction as B times angular speed" be negative?

Yes, "Friction as B times angular speed" can be negative. This can happen when the direction of the angular speed and the direction of the force of friction are opposite. In this case, the frictional force is acting to decrease the object's angular speed.

5. How does "Friction as B times angular speed" affect the motion of an object?

"Friction as B times angular speed" affects the motion of an object by slowing down its rotational motion. As the object rotates, the frictional force acts in the opposite direction of the motion, causing the object to eventually come to a stop. This is why friction is often referred to as a "dragging force" in rotational motion.

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