Proton moving towards center of ring

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Homework Help Overview

The problem involves a proton moving along the axis of a uniformly charged ring, with specific parameters regarding charge density and distance from the ring's center. The original poster expresses confusion about the initial speed required for the proton to cross the plane of the ring.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the relationship between kinetic energy (KE) and potential energy (PE) in the context of the proton's motion. There are questions about how the charge density affects the proton's kinetic energy as it approaches the ring.

Discussion Status

Participants are exploring the conservation of energy principle and its implications for the proton's motion. There is a recognition that as the proton moves closer to the ring, its potential energy decreases while its kinetic energy increases. However, the exact requirements for the proton's kinetic energy to cross the plane of the ring remain unclear.

Contextual Notes

There is an ongoing discussion about the implications of the charge density on the proton's kinetic energy and the assumptions surrounding the initial conditions of the problem.

Zarrey
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Homework Statement


A proton is moving along the main axis of a uniformly charged thin ring. The charge density on the ring is 5.0 nC / cm and the ring radius is 1.0 cm. Initially the proton is 2.0 cm (along the axis ) from the center of the ring with the velocity towards the center of the ring. What initial speed should the proton have such it will cross the plane of the ring?im a little lost on this one. any help would be wonderful.
 
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Consider PE and KE.
 
The proton needs to increase its KE to a point greater than its PE to move correct? so would i solve for the potential energy of the proton and the ring?
 
Zarrey said:
The proton needs to increase its KE to a point greater than its PE to move correct?
Doesn't sound right. It already has some PE. It needs enough KE to do what?
 
the proton needs KE in order to move. but what about the charge density? how does that play into KE when it is closer to the center of the ring? that is what i think i am confused about?
 
It doesn't need much KE merely to move. What else does it need KE for? What is happening to its PE as it gets closer? What conservation law can you apply?
 
the law of conservation of energy?

as it moves closer the PE will decrease and the KE will increase.
 
Zarrey said:
the law of conservation of energy?
Yes.
as it moves closer the PE will decrease and the KE will increase.
Why will the PE decrease?
 

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