Speed
Speed is defined as:
The distance travelled in 1 second.
It is measured in m/s or km/h (or mph in UK cars).
Speed can be calculated using:
\(\text{Average speed}=\frac{\text{distance}}{\text{time}}\)
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.
| \(\text{distance} = {speed}\times{time}\) | \(\text{d} = {s}\times{t}\) |
| \({speed} =\frac{distance}{time}\) | \({s} ={d}\div{t}\) |
| \({time} =\frac{distance}{speed}\) | \({t} ={d}\div{s}\) |
| \(\text{distance} = {speed}\times{time}\) |
| \(\text{d} = {s}\times{t}\) |
| \({speed} =\frac{distance}{time}\) |
| \({s} ={d}\div{t}\) |
| \({time} =\frac{distance}{speed}\) |
| \({t} ={d}\div{s}\) |
If a ball has a speed of 5 m/s it means that it travels 5 m every second.
Example
If a car travels 24 m in 2 seconds, what is its speed?
Answer
Speed = \(\frac{distance}{time}\)
Distance = 24 m.
Time = 2 s.
Speed = \(\frac{24}{2}\).
Speed = 12 m/s.
The car has a speed of 12 m/s.
Question
Calculate the average speed of a hockey ball if it takes 3 seconds to travel 60 m across a hockey pitch?
Speed = \(\frac{distance}{time}\)
Distance = 60 m.
Time = 3 s.
Speed = \(\frac{60}{3}\).
Speed = 20 m/s.
The average speed of the hockey ball is 20 m/s.
Question
Find the distance travelled by Caitlyn if she sprints at an average speed of 9 m/s for 4 seconds?
Distance = speed × time.
Speed = 9m/s.
Time = 4 s.
Distance = 9 × 4 = 36 m.
The distance travelled by Caitlyn is 36 m.
Question
Find the time taken to cover 256 m at an average speed of 8 m/s?
Time = \(\frac{distance}{speed}\)
Distance = 256 m.
Speed = 8 m/s.
Time = \(\frac{256}{8}\).
Time = 32 s.
The time taken is 32 s.
Question
Find the speed of a train if it covers 2 km in 120 seconds.
Speed = \(\frac{distance}{time}\)
Distance = 2 km.
Since the time is in seconds 2 km needs to be converted into meters.
2 km = 2 x 1000 m = 2000 m.
Time = 120 s.
Speed = \(\frac{2000}{120}\)
Speed = 16.7 m/s.
The speed of the train is 16.7 m/s.
Key points
- Speed is the distance travelled in 1 second.
- Speed = \(\frac{distance}{time}\).
- Speed is measured in m/s or km/h.
- If an object has a speed of 5 m/s it means that it travels 5 m every second.
