Magnitude of force (elevator question)

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Homework Help Overview

The problem involves a scenario where a person is standing in an elevator with specific velocity and acceleration parameters. The subject area relates to forces, specifically the force exerted by the elevator floor on the person, and the dynamics of motion in an accelerating frame.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • The original poster expresses uncertainty about how to begin the problem, questioning the role of acceleration and velocity in the context of forces. Other participants discuss the components of the free body diagram, including normal force and weight, and seek to clarify the resultant force equation.

Discussion Status

Some participants have attempted to derive an answer using a specific equation, while others have raised concerns about the validity of the approach and the components being combined. There is an ongoing exploration of the relationships between the forces and motion involved.

Contextual Notes

Participants are navigating the complexities of force calculations in a non-inertial reference frame, with discussions reflecting on the definitions and roles of various physical quantities involved.

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Homework Statement


Pat Summit (60 kg) is standing in an elevator which has a
velocity of 10.0 m/s downward and an acceleration of 5.00
m/s^2 upward. What is the magnitude of the force exerted by
the floor of the elevator on her? Is the elevator speeding up
or slowing down?

Homework Equations


F=ma..

The Attempt at a Solution


I really am not sure where to start here..
I drew a free body diagram but, does acceleration count as a force?
How does velocity come into play?
 
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On the free body diagram, there is normal reaction and weight. So what is the resultant force 'ma' equal to?
 
I got the answer :)
using V*m + W - F = m*a_y... so..
F = (60*9.81) - (-5m/s^2)*m + (60kg * 10m/s)
thanks for the help.
 
studybug said:
I got the answer :)
using V*m + W - F = m*a_y... so..
F = (60*9.81) - (-5m/s^2)*m + (60kg * 10m/s)
thanks for the help.

While I am glad to see that you got your answer, your equation doesn't seem to 'add' up

as

60*9.81 = N

5 m/s2 * 60kg = N

60kg*10m/s = kgm/s


which means you are adding force+force+ momentum and getting force. :confused:
 

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