We know that when an object changes its position with respect to some point of reference, the object is said to be in motion. In this blog, we are going to learn about uniform and non uniform motion with the help of examples and graphs.

Distance

An object is said to be in motion when it changes its position with respect to some stationary point called the reference point or the origin. The length of the actual path traveled by an object during its motion is called the distance traveled by the object.

For e.g., Suppose an object starts its journey from O, along with a straight line OX. A, B, C, and D are the positions of the object at different instances of time. Let the object travels from O to C and comes back to B along the same straight line. The total length covered by the object = OC + CB = 60km + (60-40) km = 80 km

This is the distance traveled by the object. Distance is a scalar quantity because it only needs a numerical value (magnitude) and a unit to describe the magnitude. There is no direction associated with distance. So during the motion of an object, the value of the distance can never be zero or negative.

Displacement

Another quantity used to describe the motion is displacement. The displacement of an object in motion is defined as the shortest distance between the initial position and the final position of the object. As in the example, where an object goes from point O to C and comes back to B. So in this case its final position is B and its initial position is O. So, the displacement of the object is only 40 km.

Displacement is a vector quantity which means it needs magnitude as well as direction for its description.

If the object comes back to its original point, the displacement will be zero.

The distinction between distance and displacement

• Distance is a scalar quantity whereas displacement is a vector quantity
• Distance traveled by an object in motion can never be zero or negative but displacement for a body in motion can be zero when initial and final positions of the object coincide.
• Distance traveled by an object is the total length of the actual path covered by the object in motion but displacement is the shortest distance between the final and the initial position of the object.

Unifor Motion

Let us consider an object moving in a straight line. Suppose the object travels an equal distance of 5 meters in the first, second, third, and fourth second respectively, and continue to do later on as well. So we can say that the object covers 5 m in each second i.e. it covers equal distance in equal intervals of time.

When an object travels the equal distance in equal intervals of time, howsoever small the interval may be the motion of the object is said to be a uniform motion.

Non Uniform Motion

We can also plot the distance-time graph for an accelerated non-uniform motion. The data represents the distance traveled by car at regular intervals of 2 seconds. Now plot the graph corresponding to the data. This graph shows the non-linear variation of the distance traveled by car with time. This graph represents a non-uniform motion. Now, look at this distance-time graph carefully.

What inference can you draw from this distance-time graph? In this graph, there is no change in the position of an object with time, which means that the body is not moving. The body is at a fixed distance of 10 m from the origin O at 1st, second, third, fourth, and fifth second. That is, the body is at rest. So, the distance-time graph for a body at rest is a line parallel to the x-axis.

Non Uniform Motion Examples

The motion of bike in a city or on a busy road. When a vehicle travels on a circular course at a constant speed, its velocity is said to be non-uniform.

Difference between uniform and nonuniform motion

The difference between uniform and non-uniform motion is listed below:

Difference between uniform and nonuniform motion

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