Graphing Motion - Position, Velocity and Acceleration

With graphing and/or the advent of calculus, not only can we calculate the average values like those calculated above, but we can also calculate an instantaneous velocity and acceleration. The instantaneous speed is what is displayed on your speedometer in your car compared to an average over the whole trip.  

Example 1 - If you drive 50 km North from Point A, to Point B in two hours what is your average speed?

Ave V = Δd/ Δt = 50kam/2hr North = 25 kam/h North
 
Does this mean that the car's velocity at any given time is 25 km/h?
 No. Read on.

 If you graph the car's position with time, the velocity at a time, t, is given by the slope of the line at the time t. Using calculus this can be expressed as

V = dd/dt

A = dv/dt

So moving from position to acceleration: to find the velocity, take the derivative (or find the slope) of the position line and to find the acceleration, take the derivative of the velocity line. In the other direction: to find the velocity, compute the area under the curve of the acceleration graph and to find the distance, compute the area under the speed graph.

Calculus also gives us relationships between position, speed and acceleration in terms of time.

d (t) = d₀ + v₀ t + ½ a t₂ if a is a constant value

v (t) = v₀ + a t