# Understanding uniform and non-uniform motion

In our everyday lives, we see many things that change their places, i.e. they move from one place to another, whether it’s living or non-living. For example, birds fly, mammals move, tables can be relocated, vehicles roll their wheels and move, etc.

Some things stay at rest while some move; therefore, those are moving and known to be in motion. A body is said to be in motion when it changes its position with respect to the body at rest. For example, when you are walking in your room, you are in motion for your study table, which is at rest.

Linear motion: If a body is moving in a straight line, it is known to be in linear motion. According to Newton, an object moves in a straight line until or unless any force is applied in any other direction.

Types of linear motion:

1. Uniform linear motion: First, we need to know what is uniform motion? When an object moves along a straight line with a constant speed, that object is known to be in uniform motion. The rectilinear acceleration of the object moving in uniform motion is zero, and the velocity of the object travelling in the straight line remains the same throughout the journey.

In other words, when the distance covered by the object remains the same in the time interval regardless of the time length, the object is known to be in uniform motion.

As we know, the slope of the distance vs time determines the speed of the object.

Slope = dy/dx = distance / time

Velocity = d/t  =10 m/s, is constant in every time interval in the above graph.

From the above context, we know when an object travelling in a straight line with a constant speed, having no acceleration, is known to be in uniform linear motion. In uniform linear motion, displacement is always equal to the distance covered.

Example of uniform rectilinear motion:

• Pendulum with equivalent amplitude on either side.
• Vibrating spring of the sewing machine.
• High-speed train on the track.
• The motion of the aeroplane in the sky.
1. Non-uniform linear motion: When an object covers the different distances in the same time intervals regardless of time length, the object is known to be in non-uniform linear motion. This type of motion always has some amount of rectilinear acceleration and doesn’t have a constant velocity.

In other words, when an object moves along a straight line without any constant speed, then the motion is called non-uniform motion.

As we can see in the above graph, every time interval has a different velocity. This is the graphical representation of non-uniform linear motion. We can say the rate of displacement varies at every instant as either the velocity increases or decreases.

In non-uniform motion, rectilinear acceleration can be negative or positive and can be zero for some instances; but can never be zero throughout the journey.

Examples of non-uniform linear motion:

• A person jogging in the park.
• Asteroide moving.
• Horse running.
• A train came to the station to stop.

Difference between uniform and non-uniform motion:

 Bases of difference Uniform motion Non-uniform motion Definition Moving with a constant velocity in the same time interval regardless of the time length Moving without any constant velocity in the time interval regardless of the time length. Rate of displacement Constant rate of displacement The rate of displacement changes every time. Average speed Average speed is always equal to the constant speed. Average speed changes as time changes. Rectilinear acceleration Rectilinear acceleration is zero Rectilinear acceleration is non-zero. Distance-time graph Always a straight line Never a straight line but curvy.

Circular motion: if a body is moving in a circular path, it is known to be in a circular motion. In other words, it can also be defined as the rotation of the object along a circular path or movement along with the circumference of a circle.

Types of circular motion:

1. Uniform circular motion: When an object is travelling at a constant speed from a centre of an axis to cover a circular path and maintain radial distance from the centre, then the object is known to be in a uniform circular motion.

Tangential and angular acceleration is zero, and the magnitude of the centripetal force is constant in a uniform circular motion. In a uniform circular motion, the angular speed and linear speed of the object remains constant. Uniform circular motion is accelerated because the velocity changes due to the change in direction continuously.

Examples of uniform circular motion:

• The motion of the earth around the sun.
• The motion of the ceiling fan’s blade.
• The motion of artificial satellites in their orbits.
• The motion of the Second hand and hour hand of the watch.
1. Non-uniform circular motion: When an object is travelling in a circular motion but has some variable angular velocity, the object is known to be in a non-uniform circular motion.

Tangential and angular acceleration is non-zero, and the magnitude of the centripetal force is not constant in non-uniform motion. In a non-uniform circular motion, the angular speed and linear speed of the particle changes with time.

Examples of non-uniform circular motion:

• The motion of the roller coaster.
• Vertical circle with string and bob.
• The motion of any object in a vertical circle.

 Basis of differentiation Uniform circular motion Non-uniform circular motion Definition Object covers a circular path with constant angular velocity Object covers a circular path without any constant angular velocity Centripetal force The magnitude of centripetal force is constant The magnitude of centripetal force is not constant. Acceleration Tangential and angular acceleration is zero Tangential and angular acceleration is non zero Kinetic energy of the particle Kinetic energy of the particle remains the same Kinetic energy of the particle varies with time. Linear speed and angular speed The linear speed and angular speed of the object remains the same The linear speed and angular speed of the object varies with time. Net linear acceleration The net linear acceleration of the object is radially inward. The net linear acceleration of the object is not radial.

Conclusion

For the above context, you can understand the two types of linear and circular motion that exist. In uniform motions, the body covers equal distance in equal time intervals, whereas in non-uniform motions body covers the unequal distance in equal time intervals. Therefore, carefully go through the concepts for using them in the proper context.