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Definition of speed

Speed is the distance travelled per unit of time. It is a scalar quantity.

If you run at 12 km/h, you will cover 12 km in one hour, 6km in half an hour, 24 km in two hours, etc.

Speed is written $$S$$ or $$v$$. It is the ratio

$$$ \Tgreen{\text{speed}} =\frac{\Tred{\text{distance}}}{\Tblue{\text{time}}}. $$$
  • A car drove 20 km in 20 minutes (1/3 hour). Its speed was $$$\frac{\Tred{20\ukm}}{\Tblue{20\umin}} =\frac{\Tred{20\ukm}}{\Tblue{1/3\uh}} = \Tgreen{60\ukmph}.$$$
  • A plane flew at 1000 km/h for 3 hours. It covered $$$ \Tgreen{1000\ukmph}\times \Tblue{3\uh} = \Tred{3000\ukm}. $$$
  • Paul ran 1 km at a speed of 10 km/h. The run took him $$$ \frac{\Tred{1\ukm}}{\Tgreen{10\ukmph}} = \frac{\Tred{1}}{\Tgreen{10}}\Tblue{\uh} = \frac{\Tred{1}}{\Tgreen{10}} \Tblue{60} \Tblue{\umin} = \Tblue{6\umin}. $$$
The ThrustSSC holds the record for the fastest speed ever recorded by a car $$(1228 \ukmph)$$
The ThrustSSC holds the record for the fastest speed ever recorded by a car $$(1228 \ukmph)$$