# Kinetic energy of a flywheel

• mikefitz
In summary, to store 1.4 x 10^9 J of energy, a 16-kg flywheel with a radius of 0.22 m would need to rotate at a speed of 85037.67 rev/min. This can be calculated using the equation for kinetic energy of a flywheel and converting radians per second to revolutions per minute.
mikefitz
A flywheel is a solid disk that rotates about an axis that is perpendicular to the disk and its center. Rotating flywheels provide a means for storing energy in the form of rotational kinetic energy and are being considered as a possible alternative to batteries in electric cars. The gasoline burned in a 387-mile trip in a typical midsize car produces about 1.4 x10^9 J of energy. How fast would a 16-kg flywheel with a radius of 0.22 m have to rotate in order to store this much energy? Give your answer in rev/min.

I know the kinetic energy of a flywheel is: http://content.answers.com/main/content/wp/en/math/1/4/8/148da762c81d0061d84cb36a21fb1e4e.png but how do I use that information to calculate how fast the flywheel needs to rotate? Thanks

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mikefitz said:
A flywheel is a solid disk that rotates about an axis that is perpendicular to the disk and its center. Rotating flywheels provide a means for storing energy in the form of rotational kinetic energy and are being considered as a possible alternative to batteries in electric cars. The gasoline burned in a 387-mile trip in a typical midsize car produces about 1.4 x10^9 J of energy. How fast would a 16-kg flywheel with a radius of 0.22 m have to rotate in order to store this much energy? Give your answer in rev/min.

I know the kinetic energy of a flywheel is: http://content.answers.com/main/content/wp/en/math/1/4/8/148da762c81d0061d84cb36a21fb1e4e.png but how do I use that information to calculate how fast the flywheel needs to rotate? Thanks
What is the definition of ω?

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Rearrange your equation to solve for omega. Do you know what each variable in that equation represents?

E=1.4*10^9 J
m=16kg
r=.22m

I=.5*16kg*.22^2 = .3872

1.4*10^9=.5*.3872*w^2

w=85037.67 rev/min?

mikefitz said:
E=1.4*10^9 J
m=16kg
r=.22m

I=.5*16kg*.22^2 = .3872

1.4*10^9=.5*.3872*w^2

w=85037.67 rev/min?
ω is in radians/second. If you had included the units in your calculation, you would have found the answer to have units of 1/s. The radians are a dimensionless quantity we add to the result because we know they were used in deriving the kinematic equations or rotation. You need to convert radians per second to revolutions per minute.

## 1. What is kinetic energy?

Kinetic energy is the energy an object possesses due to its motion. It is defined as the work needed to accelerate an object of a certain mass from rest to its current velocity.

## 2. What is a flywheel?

A flywheel is a mechanical device that stores rotational energy. It consists of a rotating mass, typically in the form of a disk or wheel, attached to an axle that can spin freely. Flywheels are commonly used in machines such as engines, turbines, and vehicles to store energy and maintain a steady rotational speed.

## 3. How does a flywheel store kinetic energy?

A flywheel stores kinetic energy through its rotational motion. When a force is applied to the flywheel, it begins to spin and gains kinetic energy. This energy is then stored in the flywheel's rotating mass and can be released when needed.

## 4. What factors affect the kinetic energy of a flywheel?

The kinetic energy of a flywheel is affected by its mass and rotational speed. A heavier flywheel or one with a higher rotational speed will have a greater amount of kinetic energy. The shape and size of the flywheel can also impact its kinetic energy.

## 5. How is the kinetic energy of a flywheel calculated?

The kinetic energy of a flywheel can be calculated using the formula KE = 1/2 * I * ω^2, where KE is the kinetic energy, I is the moment of inertia, and ω is the angular velocity. The moment of inertia is a measure of an object's resistance to change in its rotational motion, and the angular velocity is the rate at which the flywheel is rotating.

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