Chapter 7 · Physics

Speed vs Velocity

Video not playing? Watch on Instagram · YouTube

Two cars at the same 60 km/h can have different velocities. Speed tells how fast; velocity also tells which way.

Download the short notes
PDF, 214 KB · solved examples, practice set and answer key Download the workbook
PDF, 173 KB · fill in the blanks, true/false, assertion-reason, MCQ, numericals, short answer, match the columns; detailed solutions at the end Up next in this chapter

Average Speed vs Average VelocityWalk 4 km to school and back in an hour: average speed 4 km/h, average velocity zero. One uses total distance, the other displacement.Physics · simulation

Previous: Distance vs Displacement All videos in this chapter

Key points

Speed = distance ÷ time: a scalar (no direction).
Velocity = displacement ÷ time: a vector (has direction).
Same speed, opposite directions → different velocities.
Constant speed on a circle → changing velocity (direction changes).
SI unit of both: m/s; 1 km/h = 5/18 m/s.

The idea in one minute

Two cars on a highway both read 60 km/h. One heads east, the other west. Their speed is the same, but their velocity is not, because velocity includes the direction of motion.

Two cars at 60 km/h, one going east and one going west — Same speed, opposite directions: different velocities.

Distance and displacement come first

Distance is the length of the actual path. Displacement is the straight arrow from start to finish, with a direction. Speed is built on distance; velocity is built on displacement.

A wiggly path from A to B with a straight displacement arrow — Orange: the path (distance). Purple: the displacement.

Speed = distance ÷ time Velocity = displacement ÷ time

The twist: constant speed, changing velocity

A car going round a circular track at a steady 60 km/h never changes its speed, but its direction changes at every moment, so its velocity keeps changing. This is uniform circular motion, an accelerated motion.

Velocity arrows tangent to a circle at four points — Velocity is always along the tangent; its direction keeps turning.

Speed vs velocity at a glance

Point	Speed	Velocity
Formula	Distance ÷ time	Displacement ÷ time
Quantity	Scalar	Vector
Direction	Not needed	Must be stated
Can be negative?	No	Yes
Round trip average	Non-zero	Zero
SI unit	m/s	m/s

Try it yourself

Goal: See when speed and velocity agree, when they differ, and why constant speed on a circle still means changing velocity.

Pick a path: straight, there-and-back, zig-zag or circle.
Press Play (or drag the time slider) and watch the distance and the displacement arrow.
Compare the average speed and the average velocity readouts.
On the circle, watch the purple velocity arrow turn while the speed stays the same.

Open the simulation full screen

Quick quiz

5 questions. Choose an answer for each, then submit to see your score and the explanations.

More from Motion

Motion: Chapter IntroductionSitting still? With the Earth you are moving at about 1,500 km/h. Motion is a change of position with time, measured from a reference point, and this chapter gives the tools to describe it.Physics

Rest and Motion: Motion is RelativeAre you moving right now? It depends on who is watching. Rest and motion are always measured from a reference point.Physics · simulation

Position Needs an Origin and a Direction"200 m" means nothing until you say from where and which way. Position is a signed number with a unit, measured from a chosen origin.Physics · simulation

Distance vs DisplacementDistance counts the whole path you walked; displacement only looks at the straight line from start to end, with its direction.Physics · simulation