Distance and displacement
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Distance is defined as how far in total an object has travelled. Distance is a scalar quantity, meaning that it is measured only by magnitude and its direction is insignificant. It is usually measured in metres (m). Kilometres (km) can be used for greater distances, and centimetres (cm) and millimetres (mm) can be used for shorter distances.
Distance is defined as the total change in position of an object. Displacement is a vector quantity, meaning that it is measured by both magnitude and direction. It is usually measured in metres (m). The same units (m, km, cm, mm) as distance are used to measure displacement.
The motion of an object travelling in a straight line can be modelled using a velocity-time graph, where velocity is the y-axis and time is the x-axis. The area under the graph represents the displacement of the object, whereas the gradient of the graph is the acceleration. When the lines of the graph are straight, simple geometry can be used to calculate the area under the graph and thus the displacement of the object, whereas when the lines of the graph are curved, the technique of counting squares can be used instead.
Work is done when a force causes a body to move. It can be calculated using WD = Force × distance travelled in direction of force, and has units Joules (J). The distance covered by an object can be calculated when the Work Done on the object and the force being applied to it are known.
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