This calculator works out the force of friction acting on an object from the coefficient of friction and the object's mass. Friction is the force that resists sliding between two surfaces in contact, and it is everywhere: it lets us walk, grips the road under our tyres, slows machinery and wears down moving parts. The basic model is straightforward and powerful. The friction force equals the coefficient of friction multiplied by the normal force, the force pressing the two surfaces together. On level ground the normal force is simply the object's weight, its mass times gravity, so the friction force is the coefficient times mass times gravity. The coefficient of friction is a number, usually between zero and one, that captures how rough or grippy the pair of surfaces is: rubber on dry concrete is high, ice on steel is very low. This tool handles the calculation for you. You enter the coefficient of friction and the object's mass in kilograms, and it computes the normal force from the weight and returns the friction force in newtons. It also shows the friction in kilogram-force, a more intuitive everyday unit. The results update as you type, so you can see how a grippier surface or a heavier object increases the friction. Use it for physics problems, for understanding traction and braking, or to estimate the force needed to start something sliding. A useful distinction: the static coefficient, which must be overcome to start motion, is usually a little higher than the kinetic coefficient that applies once sliding. The calculation assumes a horizontal surface and is rounded for display.
Friction force = coefficient x normal force. On level ground the normal force is mass x gravity (9.81 m/s²). Assumes a horizontal surface. Rounded for display.
The friction force equals the coefficient of friction multiplied by the normal force. On a horizontal surface the normal force is the object's weight, which is its mass times gravitational acceleration of 9.81 metres per second squared. So the friction force is the coefficient times mass times gravity.
For a 10 kilogram object on level ground with a coefficient of friction of 0.5, the normal force equals its weight, 10 times 9.81, which is 98.07 newtons. The friction force is 0.5 times 98.07, about 49.03 newtons, or roughly 5 kilograms-force. A grippier surface with a higher coefficient would increase this force.
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