How Does Work Relate to Changes in Kinetic and Potential Energy?

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Homework Help Overview

The discussion revolves around the relationship between work, kinetic energy (KE), and potential energy (PE) in the context of a conservative force acting on a body. Participants are exploring how work done by a force affects changes in energy forms, particularly in a scenario involving gravitational potential energy.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to understand the connection between work done by a conservative force and the resulting changes in kinetic and potential energy. Questions are raised about the validity of the relationships W=DKE=DPE and the implications of the signs associated with energy changes.

Discussion Status

The discussion is active, with various interpretations being explored regarding the relationship between work and energy changes. Some participants have provided potential answers to the energy change question, while others are questioning the assumptions and definitions involved in the problem.

Contextual Notes

There is some confusion regarding the definitions of work and energy, particularly in the context of conservative forces. Participants are also considering the implications of the work-energy theorem and conservation of energy principles, which may not have been fully clarified in the initial posts.

yolo123
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A conservative force of 5 N causes a body to move 2 m in the direction of the force. The change of the body’s potential energy associated with the force is:
(a) zero,
(b) +10 J,
(c) -10 J, (d) infinite.

Let's say the force is pushing the body for 2m, there must be a change in KE. But, for change of KE, there must be change in PE.
I don't understand this. Can you explain to me how W=DKE=DPE?
 
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yolo123 said:
A conservative force of 5 N causes a body to move 2 m in the direction of the force. The change of the body’s potential energy associated with the force is:
(a) zero,
(b) +10 J,
(c) -10 J, (d) infinite.

Let's say the force is pushing the body for 2m, there must be a change in KE. But, for change of KE, there must be change in PE.
I don't understand this. Can you explain to me how W=DKE=DPE?
you might want to consider both the work energy theorem and the conservation of energy theorem to show the relationship between work done by a conservative force and the PE change.
 
I think I found the answer: -10J. Say it is gravity, object goes down two meters, -10J of DPE.
 
yolo123 said:
I think I found the answer: -10J. Say it is gravity, object goes down two meters, -10J of DPE.
Yes that is correct.
You should satisfy yourself (with no other non conservative forces doing work ) that the KE change is ?
 
yolo123 said:
Can you explain to me how W=DKE=DPE?

It is not. Look up the definition of potential energy. There is a minus sign there.
 
10j!
 
I did not say that your previous answer is wrong.

Is the work positive or negative?
 
Nasu, I was answering PhantomJay's question! The change in KE= +10J
 
yolo123 said:
Nasu, I was answering PhantomJay's question! The change in KE= +10J


yolo123 said:
Nasu, I was answering PhantomJay's question! The change in KE= +10J
Correct. So you originally stated that that Wc=dKE=dPE.
Do you wish to correct that statement, for the special case as in your example when only conservative forces are doing work?
 

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