Is Velocity Constant When Calculating Force in an Elevator?

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Homework Help Overview

The discussion revolves around a physics problem involving an elevator and the forces acting on a man standing inside it. The original poster presents a scenario where the elevator is rising with a constant velocity of 4.0 m/s and seeks to understand how to calculate the force exerted on the elevator, particularly in relation to gravitational acceleration.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the relationship between constant velocity and acceleration, questioning how to calculate force without knowing acceleration. Some express confusion about the implications of constant velocity on acceleration values.

Discussion Status

The discussion is active, with participants questioning the value of acceleration when velocity is constant. Some guidance has been offered regarding the definitions of acceleration and the conditions under which it applies, but no consensus has been reached on the specific value of acceleration in this context.

Contextual Notes

Participants note that the problem lacks specific information about time and distance, which complicates the calculation of acceleration. There is also a discussion about the implications of gravitational acceleration in relation to the scenario presented.

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Homework Statement


An 80kg man stands on an elevator what force is exerted on the elevator if it is rising with a

constant velocity of 4.0 m/s. (take account of grvitational acceleration g=9.8m/s^2)

Homework Equations


F=ma



3)attempt to solve

the time and distance is not given so I could not find the aceleration at all if it were it woul be merely simple addition of acceleration multiplied by the mass

F=m(g+a) what i want to know is that how can u calculate it with just the velocity?
 
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If the velocity is constant, what's the acceleration?
 
Doc Al said:
If the velocity is constant, what's the acceleration?

then the acceleration is constant aswell... but what's the value of the acceleration
 
needguidance said:
then the acceleration is constant aswell... but what's the value of the acceleration
I want you to tell me the value of the acceleration. Just think about the definition of acceleration.

Hint: It's trivial, once you realize it.
 
-___- it would be the same as when it is stationary? 9.8m/s^s...but why? if its correct
 
needguidance said:
-___- it would be the same as when it is stationary? 9.8m/s^s...but why? if its correct
Careful. When moving at constant velocity you'll have the same acceleration as when stationary. But that's not 9.8 m/s^2!

9.8 m/s^2 is the acceleration something has when it's falling. Not when it's just sitting there.
 
needguidance said:
then the acceleration is constant aswell... but what's the value of the acceleration

Is the velocity is constant, then there is no acceleration. Correct?
 

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