Uniform Circular Motion

When a body's position varies constantly with regard to a stationary object used as a reference point, it is said to be in motion. All moving bodies have one thing in common: they all change their position over time. With examples, this article discusses uniform circular motion.

What is Circular Motion and How Does It Work?

A body or object is said to be moving in a circular motion when it moves in a circle. To put it another way, motion in a circle is circular motion. When a body or object moves on a circular path, the direction of motion or speed is constantly changing. So, if an athlete moves at a constant pace over a circular path, his or her velocity will not be constant, because velocity is defined as speed in a specific direction, whereas the direction of speed here changes continuously. The motion along a circular path is said to be accelerated since the velocity changes with the continual change in direction.

If a particle is travelling in a circle, it experiences some acceleration towards the centre, causing it to rotate around the centre. Because the acceleration is perpendicular to the velocity of the particle at all times, it only changes the direction of velocity and not the magnitude. This is why the motion is uniformly circular. The force acting towards the centre is termed centripetal force, and the acceleration is called centripetal acceleration (or radial acceleration).

The acceleration in the case of uniform circular motion is:

ar = v2r = ω2r

If the particle's mass is m,

F = ma

mv2r= mω2r

This is not a unique force; in fact, a force like friction or tension could be the source of centripetal force. The force of friction between the tyres and the ground provides the essential centripetal force for moving cars on the roads.

So if a particle is in a uniform circular motion:

1) Speed is constant
2) Velocity is changing constantly
3) Zero tangential acceleration
4) Centripetal (radial) acceleration = ω2r
5) v=ωr

There is some tangential acceleration in non-uniform circular motion, which causes the particle's speed to increase or decrease. The vector sum of tangential and radial acceleration is the resulting acceleration.

Uniform Circular Motion

Consistent Circular Motion is defined as when a body moves in a circular path at a constant or uniform speed. A body can travel in a circular path at a constant speed as long as it covers the same distance in the same amount of time. However, because the direction of motion is continually changing, the velocity of a body travelling in a circle at a constant speed is not uniform.

Facts to Remember About Motion

Assume a stone is tethered to a thread and rotates in a clockwise circular route at a constant speed. When a stone reaches a given location, say A, its motion is now directed eastward. If the stone is released while it is at A, it will fly east. The stone's speed is directed south when it reaches point B. And if the stone is released at point B, it will fly off in the direction of the south. That is, when a body moves in a circular path, the speed direction at any two points is not the same. When the direction of the body's motion changes, its velocity does not remain constant.
As a result, even though the body's speed remains constant, circular motion is accelerated. Please keep in mind that circular motion requires force. Centripetal force is the force required to cause an object to travel in a circular path.

Uniform Circular Motion can also be seen in:

Artificial satellites orbit the earth in a circular motion. As a result, a satellite's orbit around the planet is accelerated.
The moon revolves around the earth in a circular pattern. The moon is a natural satellite of the earth, as we all know.
Similarly, the earth's motion around the sun can be described as a uniform circular motion. As a result, the earth's rotation around the sun is accelerated.
On a watch's circular dial, the tip of a second's hand moves in a uniform circular motion.
As a result, we realised that force is required to move the body in a circle. Uniform circular motion occurs when a body or item moves in a circular route at a consistent speed.