Finding displacement from position time graph

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Homework Help Overview

The discussion revolves around calculating displacement from a position-time graph, focusing on the change in position over a specified time interval. Participants are examining the relationship between initial and final positions within a coordinate frame.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the formula for displacement, questioning the assumptions about direction and the validity of the answer key. There is an exploration of the final and initial positions and their implications for calculating displacement.

Discussion Status

There is a consensus among some participants regarding the calculated displacement of -40 meters, but questions remain about the correctness of the answer key and the assumptions made regarding direction.

Contextual Notes

Participants note the importance of including units in their calculations and highlight the need to clarify assumptions about direction when determining displacement.

syllll_213
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Homework Statement
For e I am asked to find the displacement of the object, and I could find the total distance travelled (25m + 15m )= 40m and I assumed the direction is the same therefore it will be the displacement for the object. However the answer is -35m and I am unsure why.
Relevant Equations
distance travelled = area under velocity time graph
Screenshot 2025-06-02 at 8.52.33 am.webp
 
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Its displacement is its change in position between over the time interval. Final position ( relative to coordinate frame) minus its initial position relative to coordinate frame. What do you get for that?
 
-40?
 
syllll_213 said:
-40?
Yeah, that’s what I get too (meters-don’t forget units). So I suspect an error with the answer key.
 
Last edited:
syllll_213 said:
. . . I assumed the direction is the same . . .
No such assumption is warranted. Displacement is (final position) - (initial position).

Here, the final position is -15 m and the initial position is +25 m.
So the displacement is (-15 m)-(+25 m) = -40 m.
 

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