Frictional losses: Why does frictional torque depend on ω?

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In summary, the conversation was about a lab on rotational motion where the participants had to take into account frictional losses in their measurements. They used the relation ω=ω0*e^(-βt) to graph the values of ln(ω) vs time and found a linear relationship. They determined a value for β, indicating that the frictional torque depends on angular velocity. The concept was compared to air resistance, where the faster an object moves, the greater the force of resistance. The frictional torque in this case depends on the coefficient and force between the object and the surface, which changes as the spinning device speeds up.
  • #1
I'm doing a lab in my physics class on rotational motion. Part of the lab was understanding that the device we are working with is not frictionless, and that we will have frictional losses. We got the thing spinning at 500 deg/s, and had a device give us measurements of the angular velocity every second until it reached 150 deg/s (it took about 15 minutes).

Then, using the relation ω=ω0*e^(-βt)
where ω0 was the initial angular velocity and β is some constant.

We then graphed the values of ln(ω) vs time, and found a linear relationship:
ln(ω)=ln(ω0) -βt

Thus, from the slope, we determined a value for β, and therefore the frictional torque depends on angular velocity. However, I still don't understand why.

Can you guys help explain this?
 
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  • #2
I don't really get your question. Are you asking is to why the torque depens on omega ? That is quite straightforeward so i guess you must be meaning something else. Could you explain any further ?

marlon
 
  • #3
For the same reason air resistance depends on velocity, think of the two situations as analogous. The faster you go, the greater the force of air resistance. Are you taking a calc based course?
 
  • #4
What does kinetic friction normally depend on? The coefficient as well as the force between the object and the surface. Think about it with relation to your case. What would change the faster it spins?
 

1. What is frictional loss?

Frictional loss is the energy that is lost due to the resistance between two surfaces in contact with each other. This energy is converted into heat, sound, or other forms of energy and is a major source of inefficiency in many mechanical systems.

2. What causes frictional torque?

Frictional torque is caused by the interaction between two surfaces in contact with each other. As these surfaces move relative to each other, there is a resistance or "stickiness" that must be overcome, resulting in a torque being applied.

3. Why does frictional torque depend on ω?

The frictional torque depends on ω, or angular velocity, because as the speed of rotation increases, the surfaces in contact with each other also move faster. This increased movement results in a greater amount of frictional force, leading to a higher torque.

4. How does the coefficient of friction affect frictional torque?

The coefficient of friction is a measure of the amount of friction between two surfaces. A higher coefficient of friction means there is more resistance between the surfaces, resulting in a higher frictional torque. Conversely, a lower coefficient of friction will result in a lower frictional torque.

5. Can frictional losses be reduced?

Yes, frictional losses can be reduced through various methods such as using lubricants, reducing the surface roughness of the materials in contact, and implementing more efficient design and engineering practices. However, it is impossible to completely eliminate frictional losses as they are a natural result of the interaction between surfaces.

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