Velocity is used to describe the speed and direction of an object. If a car is traveling east at 50 km/h you know the velocity of the car, because you know both its speed and direction. Velocity is commonly represented with the units kilometers per hour (km/h).
Velocity is calculated by the relationship between an objects distance over time. Velocity is different than the speed of an object, because the direction of movement is an important element of a the calculation.
With linear motion, negative velocity could be used to describe movement to the west and positive velocity could be used to describe movement east (in the opposite direction).
v = velocity (measured in the unit km/h)
d = distance (measured in the unit km) (negative or positive distance can describe the direction of a velocity)
t = time in hours (measured in the unit h)
The formula used to describe velocity is:
v = d / t
If a plane is traveling east at a rate of 800 km (east is the negative direction) for 2 hours, what is the velocity of the plane?
v = d / t
v = -800km / 2h
v = -400km/h
The velocity of the plane is -400km/h because the plane is moving 400km/h to the east.
If the plane was traveling to the west what would the velocity of the plane be?
v = 400km/h (west has been defined as the positive direction, so there would be no negative symbol attached to the plane's velocity)