The discussion centers on the interpretation of downward acceleration in an upward-moving elevator. A downward acceleration indicates that the elevator is ascending but decelerating, approaching a stop at a higher floor. Participants emphasize the importance of defining the coordinate system, recommending that upward be treated as the positive direction for clarity. In this context, a downward acceleration of 1.4 m/s² translates to -1.4 m/s² when upward is designated as positive.
PREREQUISITESStudents of physics, educators teaching mechanics, and anyone interested in understanding motion dynamics, particularly in scenarios involving elevators and similar systems.
It means that it is going up, but slowing down. Like it is going up from the lobby and about to stop at some upper floorjwviviang said:TL;DR Summary: I just have a question (I don't know how to word this summary, sorry)
If an elevator is moving upward, what does a downward acceleration mean?
In principle you can have up be either positive or negative, whatever you prefer. However, I personally think that having up be negative is confusing, so I would recommend usually choosing up positive.jwviviang said:When applying the free body diagram, will the positive direction be upwards since the elevator is moving up?
If acceleration has a component opposite to velocity, then the object is slowing down.jwviviang said:If an elevator is moving upward, what does a downward acceleration mean?
You are free to choose the orientation of your coordinate system axes, as long you apply that convention consistently.jwviviang said:When applying the free body diagram, will the positive direction be upwards since the elevator is moving up?
A.T. said:If acceleration has a component opposite to velocity, then the object is slowing down.You are free to choose the orientation of your coordinate system axes, as long you apply that convention consistently.
I see now. So if a question says (for example) "...moving upward elevator...if the elevator has a downward acceleration a = 1.4 m/s^2..." the downward acceleration means a = -1.4 m/s^2?Dale said:It means that it is going up, but slowing down. Like it is going up from the lobby and about to stop at some upper floor
In principle you can have up be either positive or negative, whatever you prefer. However, I personally think that having up be negative is confusing, so I would recommend usually choosing up positive.
So your acceleration would be negative and your velocity would be positive.
Yes, in the usual setup with up being positive.jwviviang said:I see now. So if a question says (for example) "...moving upward elevator...if the elevator has a downward acceleration a = 1.4 m/s^2..." the downward acceleration means a = -1.4 m/s^2?