Electric Field Distribution of a disk

[davidflip]

Hi can someone help me with this problem?

A thin disc of radius 60 cm has a hole its center of radius 30 cm. A total charge of
10^-3C is distributed uniformly on its surface. Find E at a point P which is 10 cm. on the central axis of this disc.
What would be the acceleration of an electron passing through point P ?. Mass of electron = 9.11*10^-31 Kg.

How would I set up dq for this?
would it simply be dq= σ2∏rdr? and if it is what is the numerical value for σ?

Thank you!

 

[mfb]

You have a uniform charge distribution. Can you calculate the total surface area of your disk? This should give you σ.

would it simply be dq= σ2∏rdr?

If you use the symmetry of the setup, you can use that.