What is Speed and Velocity?
Speed tells you how fast something moves, while velocity tells you how fast and in which direction. Both are central to describing motion in physics and everyday life, from cars on a highway to planets in orbit.
Speed is the distance travelled per unit time, v = d/t (a scalar). Velocity is the same idea but with direction, v = Δx/Δt (a vector), measured in m/s.
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Step-by-step worked examples
A runner covers 400 m in 50 s. Find their average speed.
v = d/t v = 400/50 = 8 m/s
A car travels 180 km east in 2 hours. Find its velocity.
v = displacement/time v = 180 km / 2 h = 90 km/h east
A cyclist moves at 5 m/s for 12 s. How far do they travel?
d = v × t d = 5 × 12 = 60 m
Flashcards
Quick quiz
Q1.A car travels 240 km in 3 hours. What is its average speed?
Q2.Which quantity includes direction?
Q3.A jogger runs 100 m north then 100 m south in 40 s. Average velocity?
Q4.Speed is best described as a…
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Common mistakes
Using 'speed' and 'velocity' interchangeably in physics problems. — Correct: Speed is magnitude only; velocity requires a stated direction.
Assuming average speed and average velocity are always equal. — Correct: They only match for straight-line motion in one direction — not for round trips.
Forgetting units when reporting an answer. — Correct: Always attach units, e.g. m/s or km/h, and keep them consistent.
Treating negative velocity as 'slower'. — Correct: A negative sign shows direction, not a lower speed — the magnitude can be identical.
FAQ
What is speed and velocity?
Speed is how fast an object moves (distance/time); velocity is the same but with direction (displacement/time).
What is the speed and velocity formula?
Speed: v = d/t. Velocity: v = Δx/Δt (displacement over time), both in m/s.
How to calculate speed and velocity?
Divide the distance (or displacement) by the time taken. Use displacement and include direction for velocity.
What are examples of speed and velocity?
A car's speedometer shows speed (60 km/h); 'driving 60 km/h north' states velocity.