Particle Kinetic energy problem

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Homework Help Overview

The problem involves two charged particles, A and B, released from rest at a specific distance apart. The objective is to determine the kinetic energy of particle B when the distance between the particles changes. The subject area includes concepts of electrostatics and energy conservation.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • The original poster attempts to apply conservation of energy but expresses uncertainty about the setup and the relationship between the particles' velocities. Some participants suggest determining the forces acting on the particles and applying Newton's second law. Others question the relevance of gravitational forces in this context.

Discussion Status

The discussion is ongoing, with participants exploring different aspects of the problem. Some guidance has been offered regarding the forces involved, but there is no explicit consensus on the approach to take or the setup of the equations.

Contextual Notes

Participants are considering the effects of both Coulombic forces and gravity, with some suggesting that gravity can be neglected in this scenario. There is also a focus on the direction of forces and the need for clarity on the system's dynamics.

Punchlinegirl
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Particles A (of mass m and charge Q) and B (of mass m and charge 5Q) are released from rest with the distance between them equal to 0.9773 m. If Q = 8 [tex]\mu C[/tex], what is the kinetic energy of particle B at the instant when the particles are 2.9773 m apart? Answer in units of J.
I really don't know how to do this problem. I tried to set it up by using conservation of energy.
KE_A + KE_B + U_A + U_B = KE_A + KE_B + U_A + U_B
qkQ/.9773 + qk5Q/.9773 = KE_A + KE_B + qkQ/2.9773 + qk5Q/2.9773.
I really don't think this setup is right, and I have no idea how I would be able to solve for the final kinetic energy of B when I don't know the final velocity of A.
Suggestions?
 
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1)Start out with determining what force is acting between those particles. Also, make sure that you have the correct direction of the force vector with respect to an X and Y axis.

2)Apply Newton's second Law in both the X and Y direction.

3) Solve the equations to get the particles' velocity and positions as a function of time

marlon
 
Since the particles both have a positive charge, I know they will repel. Aside from that force, the normal force and gravity, those are the only forces I know of. Is that right?
 
Coulombic force and gravity, yes.

Though in this problem, i think you can omit gravity.

marlon
 
Wouldn't the columbic force just be in the x-dir? So it would be like
qE_b- qE_a= ma ?
Sorry... I'm still confused.
 

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