Finding acceleration from a position vs. time

[Detinator10]

Homework Statement

Given the following graph of displacement vs time for an object moving in a straight line (assume const accel):
Find the acceleration between t=0 and t=4

Homework Equations

A= ((v_i-v_f)/2)/time

The Attempt at a Solution

I've tried find the area of t=0 to t=4 in order to convert to velocity and then to acceleration. However, the problem is I don't know how to find the area because the graph is curved. I tried getting the area above the line and subtracting it from the total area of t=0 to t=4. This didn't work because I can't find the area of the hypothetical circle of which the area above the line would be a fraction of. Thanks

P.S. I know there are other questions that ask the same thing but they are either irrelevant to my particular question or went unanswered[/B]

 

[krackers]

Since you are given displacement vs. time, the derivative at a point will give you the velocity. Taking a derivative of the velocity graph gives you the acceleration.

Since the displacement graph is roughly quadratic on [0, 4] the second derivative will be a constant.

Thus you can find the instantaneous velocity at any two points, take their difference, and divide by time to get the acceleration.