Calculate the missing heat, friction force, or distance from any two known values, with units in J, cal, BTU, N, lbf, m, ft, or in.
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Heat From Friction Formula
The heat from friction calculation is based on the work done by a friction force over a distance. The calculator assumes that the mechanical work done against friction is converted into heat.
Q = F_f*d
Rearranged forms used when a different value is missing:
F_f = Q/d
d = Q/F_f
- Q = heat generated by friction, in joules (J)
- F_f = friction force, in newtons (N)
- d = distance over which the friction force acts, in meters (m)
The calculator lets you enter any 2 values and solves for the missing one:
- Heat: If friction force and distance are known, heat is found by multiplying force by distance.
- Friction force: If heat and distance are known, friction force is found by dividing heat by distance.
- Distance: If heat and friction force are known, distance is found by dividing heat by friction force.
Common Unit Conversions for Heat, Force, and Distance
The formulas use joules, newtons, and meters as base units. Other units are converted before the calculation.
| Quantity | Unit | Conversion to Base Unit |
|---|---|---|
| Heat | calorie (cal) | 1 cal = 4.184 J |
| Heat | BTU | 1 BTU = 1055.06 J |
| Force | pound-force (lbf) | 1 lbf = 4.44822 N |
| Distance | foot (ft) | 1 ft = 0.3048 m |
| Distance | inch (in) | 1 in = 0.0254 m |
Heat From Friction Reference Values
| Friction Force | Distance | Heat Generated |
|---|---|---|
| 5 N | 2 m | 10 J |
| 10 N | 5 m | 50 J |
| 25 N | 4 m | 100 J |
| 50 N | 10 m | 500 J |
Example Calculations
Example 1: Calculate heat from friction
You have a friction force of 40 N acting over a distance of 3 m.
Q = F_f*d
Q = 40*3 = 120 J
The heat generated is 120 J.
Example 2: Calculate friction force
A process produces 200 J of heat over a sliding distance of 8 m.
F_f = Q/d
F_f = 200/8 = 25 N
The friction force is 25 N.
FAQ
Does all friction turn into heat?
In a basic physics calculation, the work done by friction is treated as heat. In real systems, some energy may also go into sound, deformation, wear, or vibration. This calculator uses the ideal assumption that the friction work becomes heat.
Why is heat equal to force times distance?
Force times distance is work. When friction opposes motion, the work done against friction removes mechanical energy from the moving object. That energy is commonly converted into thermal energy, so the heat is calculated as friction force multiplied by sliding distance.
Can friction force be negative?
For this calculation, use the magnitude of the friction force as a positive value. Friction acts opposite the direction of motion, but heat generated is an amount of energy, so it is normally reported as a positive value.