Speed — Science definition
How fast an object moves, found by dividing distance traveled by the time it took.
Where it is taught
- Speed, Velocity & Acceleration — Motion, Physical Science: Matter, Forces & Energy, Grade 8
In use
Speed answers the everyday question, 'how fast is something moving?
Speed, Velocity & Acceleration
Questions using speed
Problem 1
A runner covers 100 meters in 20 seconds. What is the average speed?
Answer and explanation
5 m/s
Speed = distance ÷ time = 100 ÷ 20 = 5 m/s.
Problem 2
A train travels 300 km in 4 hours. What is its average speed?
Answer and explanation
75 km/h
Speed = distance ÷ time = 300 ÷ 4 = 75 km/h.
Problem 3
Which quantity includes BOTH speed and direction?
- distance
- velocity
- time
- mass
Answer and explanation
velocity
Velocity is speed given with a direction.
Problem 4
Explain the difference between speed and velocity using an example.
Answer and explanation
Speed only tells you how fast something is moving, like 50 km/h. Velocity tells you how fast AND in what direction, like 50 km/h north. Two cars traveling the same speed in opposite directions have the same speed but different velocities.