# How to find heat produced from friction?

1. Dec 3, 2011

### M_of_A_v_T

How do you find the heat produced from the frictional force between two objects. For example, a person roller skating on a rink or a car going at 100m/s.

2. Dec 3, 2011

### Curl

Find the work done on the friction force. That is precisely it.

3. Dec 3, 2011

### lluke9

I usually just assume that any energy lost is converted into heat energy, unless there's another important entity that's influencing the system.

4. Dec 4, 2011

### Priya123

everyone knows that everything in the world is made upn of atoms. so, take that into point. when two thing for example your hands rub each other at bthat time the atoms also rub causing a electricity like thing which produces heat.its an exothermic reaction according to thermodynamics. its as simple as it is.

5. Dec 4, 2011

### ZealScience

Energy conservation. If the car or roller skater is travelling at constant speed and there is resistance, there must be a driving force doing work without varying the kinetic energy. Since there shouldn't be other energy changing, work is done to produce heat. Therefore, you should find the work done by the driving force and that's it.

6. Dec 4, 2011

### Priya123

but is there any friction there?
i guess not

7. Dec 4, 2011

### ZealScience

What do you mean? The OP states that there is frictional force generating heat.

Or you mean the roller experience static friction which is not doing any work. But this ideal static friction is quite not realistic.

8. Dec 4, 2011

### Priya123

if u take a person driving a car for example only if the car has put up a brake will friction occur right? at that time heat is produced that i accept

9. Dec 4, 2011

### Staff: Mentor

I would calculate it. (Work done to maintain that motion on that surface) - (wind resistance on that body at that speed). Practically 100% of the difference is energy being lost as heat from friction.

10. Dec 4, 2011

### Staff: Mentor

The tyres of a car get warm/hot from travelling, even if you have not touched the brakes. The faster and more erratic you drive, the hotter they would get. To get around corners, you hope there will be plenty of friction and tyre deformation.

11. Dec 4, 2011

### rcgldr

In the case of a car traveling along a road at constant speed, the heat in the tires is due to deformation and hysteresis of the tires. There is some "squirm" related friction at the contact patch, but for simplicity, assume that the tire is purely rolling, so there is no kinetic friction. The static friction doesn't generate any heat in this case.

In the case of kinetic friction, as mentioned previously, you could assume that any losses of mechanical energy due to kinetic friction was energy being converted into heat.

There have been a few threads that calculated the energy lost to kinetic friction in the case of a sphere sliding on a frictionless surface onto a surface with friction, where the goal is to find out how much energy was lost by the time the sphere transitions into pure rolling motion with no sliding. Here's a link to one of those threads:

12. Dec 5, 2011

### Priya123

wat my point is that even though wat u said is correct the thing i dont accept is that friction occurs when two surfaces RUB EACH OTHER.it doesnt happen just like that and so both kinetic energy and potential energy is included in the subject.

13. Dec 5, 2011

### Priya123

it only rubs each other when the car has put a break after some constant driving.
and pls dont ask me how potential energy is produced over here as if think it a bit u will understand