Anything moving in a circle needs a centripetal force pointing to the centre. This free calculator solves F = mv²/r for any unknown and also gives centripetal acceleration (in m/s² and g), angular velocity, period, frequency and RPM. Use it for cars on bends, satellites, centrifuges and amusement rides.
Circular motion formulas
Worked example
A 1,200 kg car takes a 50 m radius bend at 54 km/h (15 m/s). It needs F = 1200 × 15² ÷ 50 = 5,400 N of sideways grip, an acceleration of 4.5 m/s² (0.46 g). Double the speed and the force quadruples to 21,600 N, which is why speeding round corners causes skids.
Centripetal force isn’t a new kind of force: it is provided by tension (a ball on a string), friction (tyres), gravity (orbits) or a normal force (a wall of death). “Centrifugal force” is only the apparent outward push felt in the rotating frame.
Frequently asked questions
What is centripetal force?
The net inward force that keeps an object moving in a circle, directed towards the centre. Without it, the object would carry on in a straight line.
How do you calculate centripetal force?
F = mv²/r: mass × speed squared ÷ radius. If you know rotation speed, use F = mω²r with ω = 2π × RPM ÷ 60.
How do I convert RPM to angular velocity?
Multiply RPM by 2π and divide by 60 to get radians per second. 3,000 RPM is about 314 rad/s.
How many g does a centrifuge produce?
Relative centrifugal force = ω²r ÷ 9.81. Use the RPM mode: the acceleration is shown in g.
Related tools
Free educational tool by HawkInc. Results are calculated in your browser and rounded for display; check critical work by hand or with a second method.