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

AI Thread Summary
The discussion centers on the relationship between work, kinetic energy (KE), and potential energy (PE) when a conservative force of 5 N moves a body 2 m. Participants analyze how work done by the force relates to changes in KE and PE, concluding that the change in potential energy is -10 J when considering gravity. The conversation emphasizes the importance of the work-energy theorem and conservation of energy principles in understanding these relationships. Clarifications are made regarding the definitions of work and potential energy, particularly the significance of the negative sign in potential energy changes. Ultimately, the correct interpretation of the work done and its effects on energy states is affirmed.
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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