How to Calculate Net Force on Elevator Moving Downward with Upward Acceleration?

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Homework Help Overview

The discussion revolves around calculating the net force on a person in an elevator that is moving downward while accelerating upward. The context involves understanding the forces acting on the person, including weight and acceleration due to gravity.

Discussion Character

  • Conceptual clarification, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the implications of an elevator moving downward while accelerating upward, questioning the consistency with Newton's Laws. There is discussion about the relationship between acceleration and the perceived weight on a scale.

Discussion Status

Some participants have provided guidance on the calculations presented, while others are questioning the assumptions made regarding the direction of forces and the interpretation of the scenario. Multiple interpretations of the problem are being explored.

Contextual Notes

There is a mention of a potential contradiction in the scenario, as well as differing opinions on how the forces should be represented in the equations. The original poster's understanding of dynamics appears to be a point of contention.

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Homework Statement


A weighs 600 N on an elevator when it is stationary. Each elevator accelerates according to the specified arrow that is drawn next to it. In all cases where the elevator is moving, it is moving downward.
Find net force, if the elevator is accelerating 2.0 m/s/s upward, even though the elevator is moving downward. Use g = 9.8 m/s/s


Homework Equations


w = mg
F = ma


The Attempt at a Solution


Well this is what i did: F = ma
Fn - mg = ma
Fn = ma + mg
Fn = 61.2(2) + 61.2(9.8)
Fn = 722.4 N
Is that right?
 
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That question seems contradictory. It's accelerating upward, even though it's moving downward? That isn't what Newton's Laws state.
 
well the elevator is moving downward, and if the acceleration is upward, doesn't that mean that the elevator is slowing down?
 
My apologies, you're right. I haven't worked dynamics in a while. Regardless, your work looks good.
 
So our scale weight is increasing as we're going down? Shouldnt it be decreasing? Because my teacher said, that the formula should be Fn = ma + -mg
 

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