Bicycle Wheel Friction: Average Torque Calculation

In summary, the problem involves a rotating bicycle wheel with a radius of 0.330 m and a mass of 2.00 kg. After 48.0 s, the wheel stops due to friction. The average torque due to frictional forces is found using the equation Torque = I*alpha, where I is the rotational inertia (0.1089 kg m^2) and alpha is the angular acceleration. By using the formula, the average torque is calculated to be 0.0587 N m. However, this method may not be entirely accurate as friction forces may not change linearly with respect to time. A different approach, such as using the rotational inertia as mr^2 instead of mr^2/2
  • #1
kbyws37
67
0
A bicycle wheel, of radius 0.330 m and mass 2.00 kg (concentrated on the rim), is rotating at 4.12 rev/s. After 48.0 s the wheel comes to a stop because of friction. What is the magnitude of the average torque due to frictional forces?

First I did
I = (1/2)(mr^2) = (1/2)(2kg)(0.330^2 m) = 0.1089 kg m^2

Then i used the equation
Torque = I*alpha = (I)(omega)/(time)
=((0.1089 kg m^2)(4.12 rev/s x 2pi rad/rev))/(48 s)
=0.0587 N m

however i am getting this question wrong. what am i doing wrong?
 
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  • #2
just a quick thought that your methods seem to be assuming that the torque force is changing linearly with respect to time. My quick thought says that probably isn't right (usually fiction effects are thought to be proportional to velocity, and probably that isn't linear with respect to time. Does this help you think about the problem differently?
 
  • #3
sorry, i still don't get it.
i don't know where else i would put time in
 
  • #4
kbyws37 said:
sorry, i still don't get it.
i don't know where else i would put time in
Try using I as mr^2, not mr^2/2. The rotational Inertia of a thin hoop is mr^2, which is the case here since all the mass is concentrated along the rim..
 
  • #5
thank you so much! i got it!
 

Related to Bicycle Wheel Friction: Average Torque Calculation

1. What is friction in a bicycle wheel?

Friction in a bicycle wheel refers to the resistance or force that opposes the motion of the wheel as it rolls on the ground. It is caused by the contact between the wheel and the surface it is rolling on, resulting in a decrease in speed or motion.

2. How is friction calculated in a bicycle wheel?

The friction in a bicycle wheel can be calculated by using the coefficient of friction (μ) and the normal force (N). The formula for friction is μN, where μ is a constant value that depends on the materials in contact and N is the perpendicular force that the surface exerts on the wheel.

3. What is the average torque on a bicycle wheel due to friction?

The average torque on a bicycle wheel due to friction is the force that is applied to the axle of the wheel, causing it to rotate. It can be calculated by multiplying the friction force by the radius of the wheel. The average torque is important to consider for efficient pedaling and to prevent wear and tear on the bicycle's components.

4. How does tire pressure affect friction in a bicycle wheel?

Tire pressure can significantly affect friction in a bicycle wheel. A tire with lower pressure will have a larger area of contact with the ground, resulting in higher friction. On the other hand, a tire with higher pressure will have a smaller area of contact, leading to lower friction. Therefore, it is essential to maintain the correct tire pressure for optimal performance.

5. How can friction in a bicycle wheel be reduced?

Friction in a bicycle wheel can be reduced by using lubricants, such as oil or grease, on the moving parts of the wheel. This helps to decrease the contact between the wheel and the surface, resulting in lower friction. Additionally, using high-quality bearings and properly inflated tires can also reduce friction and improve the overall performance of the bicycle.

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