Calculating the Force on a Bicycle Wheel

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SUMMARY

The discussion focuses on calculating the force exerted on a bicycle wheel given specific parameters: a radius of 32.0 cm, a mass of 1.82 kg, and a resistive force of 137 N. The problem involves determining the force F applied to the sprocket at two different radii (4.53 cm and 2.88 cm) while achieving an angular acceleration of 4.50 rad/s². Key concepts include tangential acceleration, kinetic energy equations, and the moment of inertia for a shell, defined as Mass multiplied by Radius squared.

PREREQUISITES
  • Understanding of angular acceleration and its relation to tangential acceleration
  • Familiarity with the moment of inertia for a shell
  • Knowledge of torque and its calculation
  • Basic principles of kinetic energy in rotational and translational forms
NEXT STEPS
  • Calculate the force F using the formula F = τ/r, where τ is torque and r is the sprocket radius
  • Explore the relationship between angular acceleration and torque in rotational dynamics
  • Investigate the implications of resistive forces on the overall motion of the bicycle
  • Review the concepts of linear and angular kinetic energy to understand their applications in this context
USEFUL FOR

Students studying physics, particularly those focusing on mechanics, as well as educators looking for practical examples of rotational dynamics and force calculations.

BrettF
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I have been trying this problem for a while and can't seem to figure it out:

A bicycle wheel has a radius R = 32.0 cm and a mass M = 1.82 kg which you may assume to be concentrated on the outside radius. A resistive force f = 137 N (due to the ground) is applied to the rim of the tire. A force F is applied to the sprocket at radius r such that the wheel has an angular acceleration of 4.50 rad/s^2. The tire does not slip.

a. If the sprocket radius is 4.53 cm, what is the force, F (in Newtons)?
b. If the sprocket radius is 2.88 cm, what is the force, F?
c. What is the combined mass (kg) of the bicycle and rider?

I know that the tangential acceleration a = rα where α is rotational acceleration.
I also know the Kinetic energy must be K = ½ Iω^2+ ½Mv^2 where the first term is the rotational kinetic energy and the second term is the translational kinetic energy.
Finally, I know that I which is the moment of inertia for a shell (the shape of the bicycle) is Mass*Radius^2.
I've been doing the algebra with it and can't seem to get any meaningful results. Am I on the right track with this thinking? Thanks in advance for the help.
 
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BrettF said:
I've been doing the algebra with it and can't seem to get any meaningful results.
Please show what you did (that's the point of the homework template - please do not delete it).

Working with energy is possible, but using forces and torque everywhere is probably easier.
 
The linear KE cannot be interesting because you do not know the mass of the bicycle. Concentrate on torques and angular acceleration.
 
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