Speed is the rate of change of distance with respect to time. The symbol for speed is V and the base units for speed in the metric system is [m/s]
Velocity is the vector "equivalent" of speed. The velocity of a moving object is the speed the object travels in one particular direction.
The symbol for velocity is .
Example To indicate the velocity of a transport truck going at a speed of 100 km/h to Montreal (in an easterly direction) you would write
= 100 km/h [E] ---> this is the velocity of the truck!
To calculate the average speed (or average velocity) of an object we use the general equation
Example:
If you are walking with your dog in the park at 30 cm/s. How far will you have traveled in 20 minutes?
[tip: don't forget to change units from cm/s to m/s and minutes into seconds]
[tip: when you're asked to find "how far" it means ... "find the distance"]
Given: vav = 30 cm/s = 0.30 m/s
t tot = 20 min = 20 min X 60 s/min = 1200 s
Find: dtot --> use the above equation for vav but rearrange it so that you can solve for dtot
Solution:
dtot = 0.30 m/s X 1200 s = 360 m
Therefore you and the dog would have walked a total distance of 360 m