Avstånd, tid och hastighet är fysiska storheter. Tid betecknas med t och avstånd med s och hastighet med v (alla bokstäver är gemener).
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Notes: the synonyms for distance include gap, separation, displacement, spacing, or the spatial length of a trip. The denotation s comes from from Latin "spatium" which can mean space or distance between two points.
Usually the distance is measured in metres and the time by seconds. However, often the distance unit can be the kilometre and the time unit the hour. Sometimes other units can be used such as miles and minutes.
Can you remember or calculate how many metres there are in one kilometre and how many seconds there are in an hour?
Velocity, or speed, is defined as the ratio of distance to time. In other words, velocity is calculated by dividing the displacement s by the time t that it takes to complete the displacement. The mathematical formula for velocity is
The unit of velocity is metre per second, shortened to m/s. For example the running speed of an athlete can be seven metres per second, v = 7 m/s or sometimes written 7 mps (without the slash).
Sometimes the unit of velocity can be kilometre per hour, shortened to km/h. For example the driving speed of a car can be 50 kilometres per hour, v = 50 km/h or 50 kmph.
A rabbit runs 60 metres in five seconds. Calculate its velocity.
Solution:
First, write down the numerical data for the quantities:
distance
s = 60 m
time
t = 5 s
Then, use the formula v = s/t
velocity = distance per time
and substitute the values of the quantities.
v = 60 m / 5 s = 12 m/s
It means that every second the rabbit goes as much as twelve metres away, on average.