How can we describe motion?
The speed of a moving object can be calculated if the distance travelled and the time taken are known. The faster an object moves, the steeper is the line representing it on a distance-time graph.
The velocity of an object is its speed in a particular direction. In velocity-time graphs sloping lines represent steadily increasing or decreasing velocities. Horizontal lines represent movement at constant velocities.
You should recall from your Key Stage 3 studies how to calculate the speed of an object from the distance travelled and the time taken.
When an object moves in a straight line at a steady speed, you can calculate its speed if you know how far it travels and how long it takes. This equation shows the relationship between speed, distance travelled and time taken:
For example, a car travels 300m in 20s.
Its speed is 300 ÷ 20 = 15m/s.
Check your understanding of this topic by having a go at this activity.
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