When people walk, run, or travel in a car their speed will change. They may speed up, slow down or pause for traffic.
Some typical values for speed in metres per second (m/s) include:
|Method of travel||Typical speed (m/s)|
|Car||13 - 30|
It is not only moving objects that have varying speed. The speed of the wind and the speed of sound also vary. A typical value for the speed of sound in air is about 330 m/s. A light breeze moves at perhaps 3 m/s, but a gale would be more than 20 m/s.
The speed of an object can be calculated using the equation:
The distance travelled by an object moving at constant speed can be calculated using the equation:
distance travelled = average speed × time taken
This is when:
A car travels 500 m in 50 s, then 1,500 m in 75 s. Calculate its average speed for the whole journey.
First calculate total distance travelled (x):
500 + 1,500 = 2,000 m
Then calculate total time taken (t):
50 + 75 = 125 s
Then find (v):
v = 2000 ÷ 125
v = 16 m/s
To calculate the speed of an object two measurements are needed:
These measurements can be made using different types of equipment:
|Equipment||Distance measurement||Time measurement|
|Ruler and stopwatch||Ruler measures distance travelled||Stopwatch measures time taken|
|Light gates||Size of object, measured with a ruler||Light gate connects to a timer, which gives the reading|
|Video analysis||Distance moved from frame to frame observed on a ruler in the pictures||The time between frames is known|