Two 3.0 cm diameter disks face each other, 1.9mm apart. They are charged to $$\pm 16nC$$.
(a). What is the field strength between the disks?
(b). A proton is shot from the negative disk toward the positive disk, what launch speed must the proton have to barely reach the positive disk?
I have attemped a solution for question (a), but MasteringPhysics says it is wrong.
Thanks heaps to anyone who can help
The Attempt at a Solution
My attempt at question (a):
$$A = pi * r^2$$
$$r = 0.015$$
$$Q = 16*10^(-9)$$
$$E = Q/A*Epsilon_0 = Q/A*8.85*10^(-12) = 1.278*10^6 $$