Calculating Magnitude of Forces Between Protons

[rayhan619]

Homework Statement

Two protons are 4.0 fm apart. ( 1 fm= 1 femtometer = 1*10^-15m)
a)What is the magnitude of the electric force on one proton due to the other proton?
b)What is the magnitude of the gravitational force on one proton due to the other proton?
c)What is the ratio of the electric force to the gravitational force?

Homework Equations

F = Kq1q2/r^2

The Attempt at a Solution

I figured out the 1st part. F = 14 N

but how do i start the 2nd part?

 

[LowlyPion]

b)
http://hyperphysics.phy-astr.gsu.edu/hbase/grav.html#grav