Rotational Kinetic Energy of bicycle wheels

In summary, when coasting at constant speed, the rotational kinetic energy of a bicycle's wheels is equal to 0.041/4.07 of the total kinetic energy of the bicycle and rider combined. This is calculated by adding the rotational and linear kinetic energy equations, and then taking away the w^2 in both the numerator and denominator. The result is independent of w and is equal to 0.041/4.07. It is recommended to post further questions in the appropriate forums.
  • #1
rugbygirl
5
0
A bicycle has wheels of radius 0.33 m. Each wheel has a rotational inertia of 0.082 kg* m2 about its axle. The total mass of the bicycle including the wheels and the rider is 74 kg. When coasting at constant speed, what fraction of the total kinetic energy of the bicycle (including rider) is the rotational kinetic energy of the wheels?

I thought this: Rotational KE = (1/2)Iw^2
=(1/2)(second bold number)w^2

Linear KE= (1/2)mv^2
= (1/2)(third bold number)(radius*w)^2 (i.e. plug in r*w for v)
Total KE is equal to Rotational KE + Linear KE
add the two eqns
(1/2)Iw^2/ (some # * w^2)
 
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  • #2
i think you are correct
eventually one takes away the w^2 in both numerator and denominator, then gets a result independent of w
 
  • #3
i keep getting .041/4.07 and that is not right
 
  • #4
How many wheels does a bicycle have?

Please post in the HW forums.
 

1. What is rotational kinetic energy?

Rotational kinetic energy is the energy an object possesses due to its rotational motion. In the case of bicycle wheels, it refers to the energy stored in the spinning wheels as they rotate.

2. How is rotational kinetic energy calculated?

The formula for calculating rotational kinetic energy is: KE = 1/2 * I * ω^2, where KE is kinetic energy, I is the moment of inertia, and ω is the angular velocity. In the case of bicycle wheels, the moment of inertia can be calculated using the formula: I = mr^2, where m is the mass of the wheel and r is the radius.

3. Why is rotational kinetic energy important for bicycle wheels?

Rotational kinetic energy is important for bicycle wheels because it contributes to the overall energy and momentum of the bicycle. This energy is used to keep the wheels spinning and maintain the bicycle's stability and balance while in motion.

4. How does the rotational kinetic energy of bicycle wheels affect the ride?

The rotational kinetic energy of bicycle wheels contributes to the overall smoothness and efficiency of the ride. Higher rotational kinetic energy can result in a smoother ride, while lower rotational kinetic energy may lead to more effort required to pedal and maintain balance.

5. Can the rotational kinetic energy of bicycle wheels be changed?

Yes, the rotational kinetic energy of bicycle wheels can be changed by altering the mass and/or radius of the wheels. For example, a larger wheel with a greater moment of inertia will have a higher rotational kinetic energy compared to a smaller wheel with a lower moment of inertia.

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