Calculating the Force on a Bicycle Wheel

AI Thread Summary
To calculate the force on a bicycle wheel, one should focus on torques and angular acceleration rather than kinetic energy due to the unknown mass of the bicycle. The tangential acceleration can be determined using the formula a = rα, where α is the angular acceleration. The moment of inertia for a shell is given by I = Mass * Radius^2, which is crucial for torque calculations. The resistive force of 137 N impacts the net force applied to the sprocket. A systematic approach using forces and torque will yield clearer results for the problem at hand.
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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