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Uniform circular motion
Beginner
Constant speed on a circle with changing direction.
v = ωrAn object in uniform circular motion moves with constant speed on a circle. Its velocity changes direction continuously, so it accelerates toward the centre.
A car circling at 10 m/s on a 50 m radius takes 31.4 s per lap.
Constant speed does not mean constant velocity.
In more detail
In uniform circular motion, the speed is constant but the direction of velocity changes continuously. The acceleration points towards the centre of the circle.
Real-world uses
- A car going round a roundabout at steady speed is accelerating towards the centre.
- Satellites in circular orbits move with uniform circular motion.
- A washing machine drum, a satellite in a near-circular orbit and a car on a roundabout all move in uniform circular motion.
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Frequently asked questions
Is uniform circular motion accelerated motion?
Yes, because the velocity vector is changing in direction.
What is the centripetal acceleration?
v squared divided by r, directed towards the centre.
Is an object in uniform circular motion accelerating?
Yes. Its speed is constant, but its velocity changes direction, so it has an acceleration towards the centre.
Related topics in Kinematics
Relative velocity in 2D · River-boat problems · Rain and umbrella problem · Angular displacement and velocity · Period and frequency · Centripetal acceleration