Simulation · Physics · Class 11
Average speed is not the average of the speeds
From the lesson Background: position, displacement and distance (prerequisite recap) in Motion in a Straight Line. Change the values and watch what happens.
Average speed is not the average of the speedsPhysics · Class 11
The idea behind it
NCERT § "Introduction"
- Background recap: the ideas in this block (displacement, path length, average velocity and average speed) are prerequisites the rest of the chapter builds on, summarised here so the later sections read clearly.
- Motion along a straight line is described by one coordinate x measured from a chosen origin, with one direction taken as positive; the choice is free, but it must be kept for the whole problem.
- A body can be handled as a single point (a point object) whenever its own size is negligible next to how far it travels during the motion being studied.
- Displacement is the change in position, Δx = x₂ − x₁. It carries a sign and depends only on the start and end points.
- Path length (distance) is the total length actually covered. It is never negative and is never less than the magnitude of the displacement.
- For a round trip ending at the start point the displacement is zero even though the distance covered is not.
- Average velocity is displacement divided by the time taken, while average speed is path length divided by the time taken; the two are equal in size only if the body never reverses direction.