Friction force calculator
Friction is proportional to the normal force and, to a first approximation, independent of contact area.
Rubber on dry asphalt 0.7 to 0.9; steel on steel 0.6 dry; PTFE on steel 0.04.
m/s2
Friction force
196.133N
- Normal force
- 490.3325
- Component down the slope
- 0
- Net force down the slope
- -196.133
- Angle at which it starts to slide
- 21.8014 degrees
- It slides
- 0
Show the working
- Mass = 50
- Coefficient of friction = 0.4
- Slope angle = 0
- Gravity = 9.806 65
- theta = rad(0) = 0
- Normal force = 50 * 9.806 65 * cos(0) = 490.333
- Friction force = 0.4 * 490.333 = 196.133
- Component down the slope = 50 * 9.806 65 * sin(0) = 0
- Net force down the slope = 0 - 196.133 = -196.133
- Angle at which it starts to slide = deg(atan(0.4)) = 21.8014
- It slides = 0 > 196.133 ? 1 : 0 = 0
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- friction = mu x normal force
- on a slope, normal = m g cos(theta) and the driving force is m g sin(theta)
- sliding begins when tan(theta) = mu
The angle of repose depends only on the coefficient, not on the mass, which is why a heavy box and a light one slip at the same angle.