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Change in potential and kinetic energy

  • #1

Homework Statement


how is the change in potential energy related to the change in kinetic energy?


Homework Equations


i just know that for a tossed object, the KE decreases, and its PE increases until it reaches the top. Then it has potential energy at the top, and its KE increases, while its PE decreases. im not sure how to relate the change in PE and KE though.


The Attempt at a Solution

 

Answers and Replies

  • #2
Hootenanny
Staff Emeritus
Science Advisor
Gold Member
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6

Homework Statement


how is the change in potential energy related to the change in kinetic energy?


Homework Equations


i just know that for a tossed object, the KE decreases, and its PE increases until it reaches the top. Then it has potential energy at the top, and its KE increases, while its PE decreases. im not sure how to relate the change in PE and KE though.


The Attempt at a Solution

It very much depends whether there are any non-conservative forces acting on the system. If there are no dissipative forces acting on the system then the sum of the kinetic and potential energies is constant.
 
  • #3
rl.bhat
Homework Helper
4,433
5
Tha rate of change of potential eenrgy = dp/dt = mg*dh/dt = mgv
Rate of change of kinetic energy = dE/dt = 1/2*m*2v*dv/dt = mgv.
So they are equal.
 

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