Speed
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).
\(\text{speed}=\frac{\text{distance travelled}}{\text{time taken}}\)
The distance travelled in a fixed time period, usually one second., 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 = \(\frac{\text{initial speed + final speed}}{\text{2}}\)
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 = \(\frac{\text{final speed + initial speed}}{\text{2}}\)
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:
You decide which equation to use, depending on the quantities given in the question.