Motion
What is Motion? or How to explain motion?
The change in position of an object with respect to time is called motion. Change in position is relative and it depends on the point of observation. Let's take one example to understand the change in position from different points of view. Consider Mike sitting in a moving car and Shawn standing afar. For Mike there is no motion between the car and Mike himself, if the road is smooth and Mike is not looking out, he will not know whether the car is moving or is at rest. In this case the car and the passenger both are moving together so they are stationary with respect to each other. But for Shawn standing afar and looking at the car, both are moving because there is change in position of the car with respect to Shawn i.e. from Shawn's point of view the car and Mike both are in motion.
Another example for relative motion from our everyday surroundings can be-
We are stationary when sleeping in our home but at same time we are in motion with respect to Sun because Earth is in motion with respect to the Sun.
To understand the motion we have to understand some important terms related to it. These are distance, displacement, speed, velocity and acceleration.
What is distance?
Distance is the total length of path covered between initial and final position of the object.
The image below shows a road through a forest. Since the road is curvy, the cars can not travel in a straight path between point A and B. So the length of the actual path taken by cars is called distance. You can also say distance is the total path length between two points A and B.
You can get a clear understanding of distance in the image below.
A car is traveling between two cities, New Delhi and Chandigarh. The blue line shows the distance covered by a car between two cities. It represents the total path length.
What is displacement?
Displacement is the shortest distance between initial and final position of the object.
As shown in the image above a car is traveling between two cities, New Delhi and Chandigarh. The red line shows the displacement covered by that car between the two cities. The straight line represents the shortest path length between the two cities.
What is speed?
Speed is the total distance covered per unit time between any two points. It is also defined as the rate of change of distance between two points.
Speed = Distance/ time
s= d/t
What is velocity?
Velocity is the shortest path (displacement) covered per unit time between any two points. It is also defined as the rate of change of displacement between two points.
Velocity = displacement /time
v= d/ t