Electric Field's Force on a Suspended Plastic Ball

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SUMMARY

The discussion focuses on solving a physics problem involving a 4.0-g plastic ball with a charge of Q=8 µC suspended in a uniform electric field of E=9.8 x 10² N/C. Participants emphasized the importance of using the correct charge value, noting that the accurate charge is 0.8 µC. The key equations discussed include the electric field force equation and the tangent relationship for equilibrium, specifically tan θ = (qE)/(mg), which is crucial for determining the tension force in the string and the angle of inclination.

PREREQUISITES
  • Understanding of electric fields and forces
  • Familiarity with free body diagrams (FBD)
  • Knowledge of basic physics equations involving forces and charges
  • Ability to perform calculations involving trigonometric functions
NEXT STEPS
  • Study the derivation and application of the equation tan θ = (qE)/(mg)
  • Learn how to construct and analyze free body diagrams for charged objects
  • Explore the principles of electrostatics, focusing on Coulomb's law and electric fields
  • Investigate the effects of varying charge and mass on equilibrium in electric fields
USEFUL FOR

Students studying physics, particularly those focusing on electrostatics, as well as educators seeking to clarify concepts related to electric forces and equilibrium conditions in charged systems.

EsinDerin
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Homework Statement
A small, 4.0-g plastic ball with charge Q=8uC,is suspended by a
cm-long string in a uniform electric field ⃗ E=9.8x10^2 in figure. If the ball is in equilibrium, Find
a) the tension force in the string
b) the angle between vertical axis and string.
Relevant Equations
E=k*q/r^2
k=1/4Eopi
Hi,I couldn't do this problem.I hope someone could help meths is my first time in this forum
 
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You need to show us how much you can do. You must have some idea how to solve this?
 
Welcome to the PF. :smile:
EsinDerin said:
Homework Statement:: A small, 4.0-g plastic ball with charge Q=8uC,is suspended by a
cm-long string in a uniform electric field ⃗ E=9.8x10^2 in figure. If the ball is in equilibrium, Find
a) the tension force in the string
b) the angle between vertical axis and string.
Relevant Equations:: E=k*q/r^2
k=1/4Eopi

Hi,I couldn't do this problem.I hope someone could help meths is my first time in this forum
In addition to showing your work, please try again to attach the diagram of the problem. How many cm long is the string?
 
This is the question
 

Attachments

  • Ekran Resmi 2020-04-06 23.50.56.png
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Ah, that helps. Okay, please show us your free body diagram (FBD) for the plastic ball, and write the equation for the force of the electric field on a charged body (it is similar to the equation you wrote for the electric field from a charged particle above). Please show us your work. Thanks.
 
IMG_1907.jpg

I'm not sure about the solution.If there is any mistake,please show it.Thanks :)
 
EsinDerin said:
View attachment 260181
I'm not sure about the solution.If there is any mistake,please show it.Thanks :)
It all looked good until you came to the calculation. Why didn't you do:
$$\tan \theta = \frac{qE}{mg}$$
You made a mistake writing down the charge, which is ##0.8 \mu C##.

One minor point is that you shouldn't mix vectors like ##\vec{F_e}## and scalars like ##T_x## in the same equation.
 
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Ok,are the answers are correct,I would be happy if you answer
 
EsinDerin said:
Ok,are the answers are correct,I would be happy if you answer
It's wrong because you used the wrong charge.
 

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