Electric Potential Homework: Find Q (microC) from 0.4J KE at x=0.5m

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Homework Help Overview

The problem involves a point charge Q located at the origin and a particle with a known mass and charge that is released from a specific position. The particle's kinetic energy is given at a different position, and the task is to find the value of charge Q based on the provided information.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the application of conservation of energy and the relationship between potential and kinetic energy. There is a focus on the role of mass in the calculations, with some questioning its relevance given the kinetic energy is provided.

Discussion Status

Some participants have suggested using conservation of energy principles, while others are exploring the implications of mass in the context of kinetic energy. There is an ongoing examination of the setup and assumptions involved in the problem.

Contextual Notes

Participants are navigating the constraints of the problem, including the specific values given for mass, charge, and kinetic energy, as well as the need to express the final answer in microCoulombs.

melst
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Homework Statement


A point charge Q resides at the origin. A particle of mass 0.001kg carries a charge of 6 microC. The particle is released from rest at x = 3m. Its kinetic energy as it passes x = 0.5m is 0.4J. The coulomb constant is 8.99x10^9Nm^2/C^2.
Find the charge Q. Answer in microC.


Homework Equations


I use kqQd = -k



The Attempt at a Solution


(8.99x10^9Nm^2/C^2)(6 microC)Q[(1/0.5)-(1/3]) = -0.4
Q=-4.44x10^-12

I don't know what I did wrong and is kinda confused. Can anyone help?
 
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Use conservation of energy.
[tex]U = k\frac{q_1q_2}{r}[/tex]
 
so is the mass not important??
 
Mass is important for the kinetic energy calculation. You never have to use mass though since they give you the kinetic energy. Just write an equation for conservation of energy. You start with all potential and then some of the potential energy turns into kinetic energy.
 

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