• Feb 25th 2013, 02:19 PM
sakonpure6
I am starting to panic....

How do you find the average velocity from a Velocity-time graph. The graph has a slope of 0.75 and starts at (0,6) and ends at (8,12)

I calculated V.avg = 9. (( 6+ 12)*0.5) but the answer sheet says 12? How?

And, in general how do you find the acceleration from a position- time graph?

edit: I was looking at the wrong answer sheet >.< for the first part it is 12!
but I still don't know how to find the acceleration from a position - time graph, easily. I know I am supposed to find the instantaneous velocity at several points and then construct a velocity - time graph. But is there an easier way?
• Feb 25th 2013, 03:01 PM
ILikeSerena
Hi sakonpure6! :)

Quote:

Originally Posted by sakonpure6
I am starting to panic....

How do you find the average velocity from a Velocity-time graph. The graph has a slope of 0.75 and starts at (0,6) and ends at (8,12)

I calculated V.avg = 9. (( 6+ 12)*0.5) but the answer sheet says 12? How?

edit: I was looking at the wrong answer sheet >.< for the first part it is 12!

If the velocity is 6 at the beginning and 12 at the end, the average velocity can hardly be 12!?!
Your answer of 9 is correct based on the information you gave.
It does require constant acceleration, but you have that, since it's a straight line.

Quote:

And, in general how do you find the acceleration from a position- time graph?

but I still don't know how to find the acceleration from a position - time graph, easily. I know I am supposed to find the instantaneous velocity at several points and then construct a velocity - time graph. But is there an easier way?
Nope. That's the way to do it.
If the acceleration is constant, you only need 2 instantaneous velocities though.
• Feb 25th 2013, 03:33 PM
sakonpure6