Solving a Sphere Problem: Help Needed for Physics Assignment

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Homework Help Overview

The discussion revolves around a physics problem involving a sphere with a specified mass and charge, suspended between two charged plates. The problem requires determining the angle of the thread from which the sphere hangs when a voltage is applied across the plates.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants are discussing the forces acting on the sphere, including gravitational and electric forces. There are attempts to relate the electric field to the voltage and distance between the plates. Questions about the relationship between the angle of the thread and the forces involved are also raised.

Discussion Status

Some participants have provided guidance on calculating the electric field and relating it to the forces acting on the sphere. There is an ongoing exploration of the concepts involved, with multiple interpretations being considered, particularly regarding the setup of the problem and the relevant equations.

Contextual Notes

The original poster expresses difficulty with the language barrier and understanding the problem, which may affect the clarity of their questions and responses. The problem involves specific values for mass, charge, voltage, and distance, which are crucial for the calculations but may not be fully understood by all participants.

hrappur2
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Hello everyone!

I'm trying to solve some physics problems for my school and I'm very bad at it. I've only 1 problem left and I would appreciate it if you guys could point me in the right direction. But I want to say that I'm not from an English speaking country so I'll have to translate the problem, it could be hard but I will try my best.

So here it is:

There is a little sphere with the mass 25g and 50nC, it hangs vertically on a thread between two plates and there is 10cm between the plates. Then 131 V are put on the plates so that the sphere pulls(?) to one of the plates. What angle does the thread of the ball (or and the ball) make? (The last sentence has wrong grammar in my own language so it could be wrong but I hope you can understand it).

-Thanks in advance!
 
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Hi hrappur,

See attached picture. Is that the problem?

Show what you think about the problem. What forces act on the ball?

ehild
 

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Thanks for your reply ehild!
I'm trying to figure this out but I just can't, if stuff doesn't fit perfectly into formulas I just get so lost :(

I got some ideas but they are probably stupid. Should I find what E is and than find s to find how long the ball has moved?
 
Show what you think.
Yes, find E first.
The resultant of the electric force and gravity is opposite to the force of tension in the string. The yellow angles are equal. How is the angle related to the forces?

ehild
 
I can't figure this out :(
 
Do you know the electric field?

ehild
 
is it E = k(Q/r^2) = (9*10^9)*((50*10^-9)/(10*10^-2)^2) = 4,5*10^4 N/C?
 
It is the electric field around a point charge. Here you need the electric field between the parallel plates. This electric field acts on the charge of little sphere.

Given the voltage (131 V) between the plates which are 10 cm apart. The field is homogeneous. How are the voltage and electric field related?

ehild
 
So E = V/d and than F = qE? Well I don't know
 
  • #10
hrappur2 said:
So E = V/d and than F = qE?
That looks right.
 

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