Scientists often make measurements. The physical quantities they measure fall into two categories: scalars and vectors. Scalar and vector quantities are treated differently in calculations.

Part of

Speed is a measure of how fast something is travelling.

It is the distance travelled in 1 second (or in 1 hour).

Speed is measured in m/s or km/h (or mph in UK cars).

Speed, or distance, or time can be calculated using the dst triangle.

Cover the letter you want to find to get the formula you need.

- d = s × t
- s = d ÷ t
- t = d ÷ s

- Question
If a car travels 24 m in 2 seconds, what is its speed?

Speed = distance travelled ÷ time

24 m ÷ 2 s = 12 m/s.

The car has a speed of 12 m/s.

If the

**initial speed**and the**final speed**of an object are known, then the average speed of the object over the journey can be calculated using the equation:Average speed =

- Question
A car travelling at 22 m/s increases its speed to 30m/s. Find its average speed over the journey.

Final speed = 30 m/s

Initial speed = 22 m/s

Average speed =

Average speed = (22 m/s + 30 m/s) ÷ 2 = 52m/s ÷ 2 = 26 m/s.

The average speed of the car is 26 m/s.

**There are two equations for average speed:**

Average speed =

Average speed =

**You decide which equation to use, depending on the quantities given in the question.**