Calculate Velocity from a P vs T graph

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To calculate the velocity from a P vs T graph, the slope of the curve at the desired time must be determined. The correct formula for velocity is derived from the slope, which is calculated as the change in position over the change in time. In this case, using points (1.5, 30) and (2.5, -30), the slope yields -60 cm/s. This method clarifies the discrepancy between the initial calculation and the correct answer. Understanding how to find the slope is crucial for accurate velocity determination.
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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!
 

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Hi twalk353! Welcome to PhysicsForums :smile:

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

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