How do i determine instantaneous velocity and average velocity from certain times on a graph?

Question

How do i determine instantaneous velocity and average velocity from certain times on a graph?

Answer 1

Instantaneous: Find the derivative of the motion function.

Average: Divide the whole distance traveled  by the whole time.

Answer 2

Velocity is a vector quantity which is displacement/time in a direction.

On a distance vs time graph, construct a tangent to the curve at a given point and determine the slope. This will be the instantaneous velocity at that point.  

Average velocity is displacement over total time. Select two points and use the equation:

(d2 - d1) / (t2 - t1)

where:

d2 = displacement after time t2

d1 = displacement after time t1

Here are decent descriptions:

Average Velocity:

http://theoryx5.uwinnipeg.ca/physics/one...

Instantaneous velocity:

http://theoryx5.uwinnipeg.ca/physics/one...