Speed is a measure of ‘how fast’ you are going it is a scalar quantity.
| Definition: Speed |
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| Speed is defined as the rate of change of distance |
SI units are metres per second, though many other non standard units are used such as kilometres per hour.
The speedometer on a car tells you how fast the car is travelling at that particular instant in time. It is known as the instantaneous speed.
The speedometer shows an instantaneous speed of 67 km/h.
If the whole car journey is looked at we may be more interested in the average speed.
| Average Speed |
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| Average speed is calculated by (total distance ÷ total time) |
In equation form:
<v> =  |
The current world record for the 100 m sprint is Usain Bolt at 9.58 s.
- What is his average speed for the race?
- What was his slowest instantaneous speed during the race?
- What can we say about his fastest instantaneous speed during the race?
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