Why Is the Force Acting on the Object -3k When x=0?

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Homework Help Overview

The discussion revolves around the calculation of force acting on an object based on its potential energy function, U(x)=0.5kx^2+3kx. Participants are exploring the implications of the force being -3k when x=0, as well as the relationship between potential energy and kinetic energy.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants are attempting to derive the force from the potential energy function and are questioning the sign of the force at a specific position. There are discussions about the relationship between work, kinetic energy, and potential energy, as well as the implications of total mechanical energy on kinetic energy.

Discussion Status

Some participants have provided insights into the relationship between potential energy and force, while others are questioning the implications for kinetic energy. Multiple interpretations of the problem are being explored, but there is no explicit consensus on the overall understanding of the kinetic energy in this context.

Contextual Notes

There is a lack of specification regarding total mechanical energy, which is influencing the discussion about kinetic energy. Participants are also navigating the implications of the derived force and its relationship to potential energy without a complete resolution.

UrbanXrisis
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The potential energy of an object is given by U(x)=0.5kx^2+3kx, where U is joules, x is in meters and k is a constant. What is the force acting on the object when x=0?

PE=Fd
0.5kx^2+3kx=Fd
0.5kx+3k=F
F=3k

The answer is -3k, why?
 
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Recall Work = -(delta)PE

Fd = -(0.5kx^2 + 3kx)
F = -0.5kx - 3k
F = -3k , x = 0
 
what is work for KE?

W=.5mv^2
or
W=-.5mv^2
 
The relationship between the potential function and the force is this: [itex]F = - dU/dx[/itex].
 
would the object's Kinetic energy be positive then?
 
UrbanXrisis said:
would the object's Kinetic energy be positive then?
Beats me. That depends on the total mechanical energy, which you have not specified.
 

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