Finding Velocity on a Position/Time Graph

  • Thread starter 5pirit
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  • #1
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Hey everyone, i'm having trouble finding velocity on a straight line position/time graph. Every single equation I do ends up with a different answer, which doesn't make sense because it's a straight line.

I know the equation is

Vf-Vi/Tf-ti

The answer to this question is 1.4m/s N

Example:

45-25/28-16= 1.666666m/s Wrong answer. I'm just taking these from the graph by the way.

25-20/16-14= 2.5, completely different answer.

Could someone please explain what i'm doing wrong? I'm calculating the slope which seems to change with every calculation that I do, which I understand is wrong.
 

Answers and Replies

  • #2
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Try to post the graph so we can see it. Also, if your v is velocity, you are dividing a velocity change by an elapsed time. That gives acceleration. If you want velocity, divide displacement by time.
 
  • #3
SammyS
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Hey everyone, i'm having trouble finding velocity on a straight line position/time graph. Every single equation I do ends up with a different answer, which doesn't make sense because it's a straight line.

I know the equation is

Vf-Vi/Tf-ti

The answer to this question is 1.4m/s N

Example:

45-25/28-16= 1.666666m/s Wrong answer. I'm just taking these from the graph by the way.

25-20/16-14= 2.5, completely different answer.

Could someone please explain what i'm doing wrong? I'm calculating the slope which seems to change with every calculation that I do, which I understand is wrong.
Hello 5pirit. Welcome to PF !

What is the slope of that line?
 

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