How Is the Mass of a Charged Particle Determined in an Electric Field?

AI Thread Summary
To determine the mass of a positively charged particle suspended in an electric field, the relationship between force, charge, and electric field strength must be considered. The particle's charge is given as 9.35 pC, and the electric field is generated by two charged plates. The participant initially calculated the mass using the charge-to-proton mass ratio but arrived at an incorrect value. The correct approach involves equating the electric force (F = qE) to the gravitational force (F = mg), leading to the formula m = (q/g) * |E|. This method clarifies the calculation, resulting in the correct mass of 4.9 x 10^-4 kg.
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Homework Statement


A positively charged particle (9.35pC) is suspended in equilibrium in an electric field between two horizontal parallel plates with opposite charges. Each one of the square plates has a charge of 5.5x10^-5C; and are separated by 6.25mm and their sides are 11cm long
what is the mass of the particle?

Homework Equations


E=kq/r^2
n=q/qp
idk...

The Attempt at a Solution


first i divided the charge of the particle by the elemental charge
9.35x10^-12/1.602x^-19
i got 58364544
then i multiplied this number by a protons mass
58364544*(1.673x^-27)
i got 9.764x10^-20

the book says the answer is 4.9x10^-4
soo confused!
 
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Consider the E-Field between the plates.

What does that come to?

You know that F = q*E

And you also know F = m*g

So ...

m = (q / g) * |E|
 
wow, i feel like a moron for not seeing that! thanks!
 

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