Start here

A bus leaves a stop. A minute later the bus is far away. How do you say clearly what happened?

This is Chapter 4 of your Class 9 book, Exploration. It is called Describing Motion Around Us. Numbers and graphs will do the describing.

What you will learn

• Where it is — position from a reference point.
• How far, and how far from — distance and displacement.
• How fast — average speed and average velocity.
• Speeding up — acceleration.
• Steady and changing — uniform and non-uniform motion.
• Reading a graph — what slope tells you.
• Area under the line — displacement, and three equations.
• Round and round — steady speed on a circle.

Need a quick recap?

You met these ideas in earlier classes.

• Speed — distance divided by time.
• Motion in a straight line — a car on a straight road.
• Drawing a line graph — one thing on each axis, with scales.

Begin with the plainest question. Where is the bus?