Potential Difference and Kinetic Energy

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Homework Help Overview

The discussion revolves around a physics problem involving the kinetic energy of a helium nucleus as it moves through a potential difference. The subject area includes concepts of electric potential and kinetic energy in the context of charged particles.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to relate kinetic energy and potential difference using equations like E=qv and 1/2 mv^2. Some participants suggest focusing on the simpler equation E=qv and emphasize the importance of considering the signs associated with the potential difference.

Discussion Status

The discussion is active, with participants providing guidance on the relevant equations and the importance of sign conventions. There is a recognition of the need to visualize the scenario to understand the energy changes involved.

Contextual Notes

Participants are navigating the implications of a negative potential difference and how it affects the kinetic energy of a positively charged particle. There is a mention of the initial kinetic energy and how it relates to the potential energy change.

aimeemarie
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Hello out there! I am having trouble figuring out how to set this up:

A helium nucleus (charge +2e) moves through a potential difference V = −0.70 kV. Its initial kinetic energy is 3.80 10-16 J. What is its final kinetic energy?

I feel like I should be using 1/2 mv^2=qV or E=qv. I feel like maybe I am close but I am getting lost. Can anyone help explain this please??
 
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Welcome to PF!

Just use E=qv. You aren't asked for velocity. Remember E=qv will be added onto the initial energy.
 
Be sure to keep track of your negative signs.
Given you have a negative charge moving through a net negative potential difference...visualize: your nucleus moves from 0.7V (+) to 0V (-). Is it going to slow down (lose kinetic energy) or speed up (gain energy, the field associated with that voltage doing work on it) as it moves through that difference?
 
I can't believe I didn't think to add them together, thank you :)
 

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