Question

Define motion. What do you understand by the terms ‘uniform motion’ and ‘non uniform motion’? Explain with examples. (a) Define speed. What is the SI unit of speed? (b) What is meant by (i) average speed, and (ii) uniform speed.

Answer 1

Hint: First of all, write down the terms that need to be defined. As per the question, start with the definition of “motion” and then explain it with an example. Then define the types of the motion. There are two mainly two types of motion (1) uniform motion and (2) non-uniform motion. Now, define speed with SI units and then define average speed and uniform speed.

Complete solution:
Motion: Motion is the rate of change of position of an object. For example motion of a vehicle on a highway.
Uniform motion: When an object covers equal distance in equal interval of time and moves in a straight line then the object is said to be in uniform motion.
For example: If the speed of a vehicle on the road is \[{\text{20 m/s}}\], it means that the car covers 20 meters in one second. The speed is constant in every second.
Non uniform motion: When an object moves unequal distance in equal interval of time then the object is said to be in non-uniform motion.
For example: If a vehicle on road covers 20 km in the first hour and the next 10 km in the next 3 hours.
(a) Speed: Speed is the measure of the motion of the body. Through the knowledge of speed, we can easily check whether the object is moving fast or slow with respect to some object.
Speed is a scalar quantity.
SI unit of speed is ${\text{m/s}}$.
(b) (i) Average speed: Average speed is the total distance travelled by the body in total time. Average speed can also be defined as the ratio of the total distance travelled by the body to the total time of the journey.
Formula: ${\text{Average speed = }}\dfrac{{{\text{total distance travelled}}}}{{{\text{total time taken}}}}$
(ii) Uniform speed: When an object or vehicle covers an equal distance in equal interval of time then the motion is said to be uniform speed.
For example: If the distance between Delhi and Jaipur is 300 Km and the body covers first 100 km in 2 hours and the body covers next 100 km again in 2 hours and last 100 km in 2 hours then the total distance covered by the body in each hour is equal. However, practically it is not possible as in some areas particularly in Delhi so much traffic jam is there and some areas are clean to move with high velocity without any interference.

Note: When an object or vehicle covers unequal distance in equal interval of time or covers equal distance in unequal interval of time, then the body is said to have non-uniform speed or variable speed.
For example: If the distance between Uttar Pradesh and Bihar is 600 Km and the body covers the first 200 km in 3 hours and next 100 km in 2 hours and the last 300 km in just 3 hours then the total distance covered by the body or object is the same but has an unequal time interval. This is the practical case. We can observe the cases of variable speed in our surroundings daily.