AQA GCSE Speed
Speed
Speed is the distance (metres) an object travels in one second.
Speed has units of metres per second, or m/s
Speed is a scalar quantity, so it has a magnitude, but no direction.
Uniform and non uniform speed
Uniform speed means that the speed is constant and it does not change. An example is a car travelling along a road at a constant speed of 10m/s.
In real life uniform speed is unrealistic. This is because most of the time when an object is moving it will increase or decrease its speed.
Non-uniform speed means that the speed will change, so it can increase or decrease. An example could be a person going for walk at 1.5m/s, then run at 3m/s, then return to walking at 1.5m/s for the remainder of their journey.
In real life non-uniform speed is more realistic as it represents real life examples better.
Typical speeds
The following table will give you examples of different typical speeds.
It is important to understand that there are different factors that could affect the values in the table below.
If a person is walking up a hill, there speed is likely to be less than 1.5m/s, or if the person is elderly, then value may be less than 1.5m/s
| Motion | Speed (m/s) |
|---|---|
| Walking | 1.5 |
| Running | 3 |
| Cycling | 6 |
| Car | 12 |
| Bus | 10 |
| Train | 25 |
| Aeroplane | 250 |
| Wind speed | 3 |
Speed of Sound in air
Speed of sound in air has a typical value of 330m/s
However, this value varies:
1. Temperature decreases, speed of sound in air will decrease as the particles have less kinetic energy, so sound wave is transferred more slowly.
2. At higher altitudes, temperature decreases, so speed of sound of air will decrease.
Practice Questions
1. Define the term Speed
2.Explain the difference between uniform and non uniform speed.
3. Draw a bar chart to compared the different speeds that allows a comparison for walking, running, cycling, running, car, train and bus
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