Calculate Velocity from a P vs T graph

[twalk353]

Homework Statement



What is the velocity of the object at t=2.5 s?
Please see attached graph.


Homework Equations

v = d / t

The Attempt at a Solution

v = -30cm / 2.5 s = -12cm/s

key gives correct answer as -60cm/s, but I can't figure out how to get that answer. Please help!

 

[Infinitum]

Hi twalk353! Welcome to PhysicsForums

To find the velocity, you need to find the slope of the curve at that point. How would you do it?

 

[twalk353]

Hi Infinitum! Thank you...

Eureka! That simple...I knew I was over looking some thing very easy.

slope = rise / run -or- y2-y1 / x2-x1

(x1,y1) could be (1.5,30) or (2,0) and (x2,y2) could be (2.5,30)

Then plug in...
-30-0 / 2.5-2 = -60cm/s!

Thank you for your help!