# The Amount of Joules generated by a car wheel travelling at 30mph

1. Jun 27, 2012

### Redvers

I am interested to know the amount of Joules created by an average size car wheel travelling at 30mph. Please could you let me know the calculation needed to work this out?

Thank you,

2. Jun 27, 2012

### Staff: Mentor

why not use E = 1/2 m v^2 to get it? You know the mass of the car and you know its speed.

3. Jun 27, 2012

### nasu

What makes you think that the car wheel is creating any amount of Joules?
What process do you have in mind? There is no known process for energy creation.
The energy may be transferred between systems and transformed from one form to another.

4. Jun 27, 2012

### Karimspencer

Energy can't be created nor destroyed however it can be transformed from one form to a another. Lets say the mass of the car was 500 kg and the speed is 30 miles per hour which is 13.4112 meters per second so KE=1/2 mv-squared =1/2*500*13.4112 meters per second squared= 44965.07136 joules

5. Jun 27, 2012

### nasu

How would this answers the OP question about the energy "created by an average size car wheel"?

6. Jun 28, 2012

### Redvers

Thank you but wouldn't you need to consider the weight of the alloy and tyre? The average car wheel weighs 15kg.

7. Jun 28, 2012

### Karimspencer

I thought he said car, my bad.

8. Jun 28, 2012

### Staff: Mentor

The kinetic energy of the tire is a small fraction of the kinetic energy of the car, as the tire's mass is usually a small fraction of the total car mass.
As the tires are rotating, their kinetic energy per mass is larger, the value depends on the internal mass distribution: A solid disk would have 50% more kinetic energy, a circle (and nothing inside) would have 100% more. This assume that the tires are rolling and not slipping ;).

9. Jun 28, 2012

### Karimspencer

In case of the wheel , lets say the mass is 15 kg
so the K.E = 1/2*15*13.4112 meters per second squared=1348.9521408 J