Understanding Position-Time Graphs: Can They Determine Speed?

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Discussion Overview

The discussion centers around the relationship between position-time graphs and their ability to determine speed and velocity. Participants explore the definitions and implications of these concepts in the context of one-dimensional motion.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions whether a position-time graph can determine speed, suggesting it may only indicate velocity.
  • Another participant asserts that speed is the magnitude of velocity, implying that if velocity can be determined, speed can also be derived.
  • A third participant clarifies that in one-dimensional motion, a position vs. time graph provides both speed and velocity, with the slope indicating direction.
  • A later reply emphasizes that the slope of the tangent line on the graph represents instantaneous velocity, while the absolute value of that slope corresponds to speed.

Areas of Agreement / Disagreement

Participants express differing views on whether position-time graphs can solely determine speed or if they also provide velocity information. The discussion reflects a lack of consensus on the initial question posed.

Contextual Notes

The discussion assumes one-dimensional motion but does not explore the implications of multi-dimensional scenarios. There are also unresolved nuances regarding the definitions of speed and velocity.

noodles
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Can the position-time graph tell you the speed?
I thought it was ONLY velocity.

Can you please give me an example when IT DOESN'T allow you to find the speed?

Thanks so much in advance!
 
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Speed is the magnitude of the velocity, if you can find the velocity you can always obtain the speed.
 
Presumably we are talking about motion in one dimension, otherwise it's not clear what the position axis represents.

In which case a graph of position vs time gives you speed and velocity. The direction component of velocity comes from the slope of the line. +ve slope is away from the origin, -ve slope is towards the origin.
 
Just to piggyback for additional clarity: if you find the slope of the tangent line on a position vs. time graph you have found the velocity at that instant. The absolute value of the slope is the speed.
 

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