## Speed

The speed of an object is a measure of how fast it is moving.
(Velocity is the same value as the speed but also includes the object's direction.)

Speed tells us how far (the distance) the object moves in a certain time.
Because speed changes often over a journey, we usually mean AVERAGE speed.

If the distance is measured in kilometres and the time in hours the speed will be given in km/hr (kilometres per hour)

The formulas used to calculate the speed, distance and time are:

 This meansSpeed = Distance ÷ Time Example A car travels from Christchurch to Dunedin a distance of 360 km.The journey takes 4 hours. What is the average speed of the car? Speed = Distance ÷ Time = 360 ÷ 4 =90 km/h This meansTime = Distance ÷ Speed Example A plane flies from Auckland to Invercargill a distance of about 1600 km.The average speed of the plane is 400 km/h. How long does the journey take? Time taken = Distance ÷ Speed = 1600 ÷ 400 = 4 hours 200 metres

For an exciting and fun practice with these formulae −