Uniform Circular Motion with Examples

Key Concepts

• Uniform circular motion
• Timeperiod

Introduction: 

In this session you are going to read about uniform circular motion and relate radius of the circle formed during circular motion, speed of the object and the time period. 

Explanation: 

Uniform Circular Motion 

It is the motion of an object traveling at a uniform speed on a circular path.  

1. It can be uniform with constant speed. 

2. It can be non-uniform with the change in rate of rotation. 

In a uniform circular motion, the speed or the magnitude of the velocity is constant. 

Direction of the velocity vector is not constant. Since there is a change in direction, there is acceleration. 

Time period 

Time period in a uniform circular motion is the time required to travel once around the circle, that is to make one complete revolution. 

T =

2πrv2πrv

Where, r is the radius of the circle formed, 

v is the velocity of the moving object, and 

T is the time period of one revolution. 

Examples of uniform circular motion: 

1. Motion of artificial satellites around the earth.

2. Motion of electrons around the nucleus in an atom. 

3. Motion of blades of a windmill.  

d. Motion of the second, minute and hour hand in a watch or a clock. 

Questions and answers 

Question 1: List a few examples of uniform circular motion from your daily life. 

Answer: 

A few examples of uniform circular motion from daily life are: 

• Satellites orbiting around the earth. 

• Revolution of earth around the sun. 
• Driving a car on a circular path. 
• Giant wheels in an amusement park. 

Question 2: What is the time period of motion of a boy in a merry-go-round if the radius of the merry-go-round is 20 m and the speed of the boy around the merry-go-round is 40 m/s.  

Answer: 

Radius of merry – go – round = 20m 

Speed of boy = 40 m/s 

According to formula, T =

2πrv2πrv

= 2 × 3.14 ×

20402040

= 3.14 s 

Question 3: The wheel of a car has a radius of 0.34 m and is being rotated at 900 revolutions per minute (rpm) on a tire balancing machine. Determine the speed in standard units at which the outer wheel of the car is moving. 

Answer: 

Answers: 

900 revolution in 1 minute 

So 1 revolution in

19001900

min =

19001900 × 60 

= 0.07 s 

∴ ∴ 

Time period = 0.07 s 

Radius = 0.34 m 

According to formula, T =

2πrv2πrv

2 × 3.14 × 0.340.072 × 3.14 × 0.340.07

= 30.5 m/s  

Summary

• Uniform circular motion is the motion of an object traveling at a uniform speed on a circular path.
• There is acceleration in uniform circular motion.
• Time period in a uniform circular motion is the time required to travel once around the circle, that is to make one complete revolution.

T=2πr/v​

• A few of the applications where this is used is:

1. Satellites orbiting around earth.

2. Revolution of earth around sun.

3. Driving a car in a circular path.

4. Giant wheels in an amusement park.