Electric field for point charge

[tuggler]

Homework Statement

You charge a piece of aluminum foil (mass = 4.65 g) by touching it to a charged rod. The charged rod gives the aluminum foil a charge of 10 µC. Your professor brings a charged plate over and tells you to put the aluminum foil on top of the plate. To your surprise the aluminum foil hovers motionless in the air above it! Calculate the value of the electric field from the charged plate (assume it is a uniform field and the aluminum foil is a point charge).

Homework Equations

F = Eq and F = ma

The Attempt at a Solution

What I did was first calculate the gravitational force with the equation F = ma = (9.8m/s^2)(4.65g) = 45.6 N. Then I use the equation F = Eq \implies E= F/q, where E = electric field, q = charge, and F = force.

Thus F = 45.6, q = 10e-6 \implies 45.6N/(10e-6 µC ) = 455700 N/C.

But it is wrong. What did I do wrong? Thanks in advance!

 

[voko]

What I did was first calculate the gravitational force with the equation F = ma = (9.8m/s^2)(4.65g) = 45.6 N.

Do grams times meters per seconds squared give Newtons?

 

[tuggler]

No, it does not, but kilograms over s^2 does.

 

[voko]

So what's the correct weight then?

 

[tuggler]

It is 4557 N/C. THANKS!