(a) Two protons in a molecule are 3.90 10-10 m apart. Find the electric force exerted by one proton on the other.
direction: attractive or repulsive
(b) State how the magnitude of this force compares with the magnitude of the gravitational force exerted by one proton on the other.
(c) What must be a particle's charge-to-mass ratio if the magnitude of the gravitational force between two of these particles is equal to the magnitude of electric force between them?
you are comparing the ratio of the electric force to the gravitational force, which is given by the formula below:
where G is your gravitational constant which equals: 6.674*10^-11 N*m^2/kg^2
and m1 and m2 are the mass of the particles which are each: 1.673*10^-27kg
and r is once again 3.9*10-10 m.
The gravitational force is found to be: 1.228*10^-45 N
Now the ratio would just be your answer from Part A divided by 1.1228*10^-45 N,
which would result in 1.238*10^36 as the answer.
you are finding the ratio of the charge to the mass, or q/m.
To do this set the equations for the gravitational force equal to the equation for the electric force as follows:
(G*m1m2)/r^2 = (ke*q1q2)/r^2
now move the variables around until you have a ratio of q/m,
q/m = 8.616*10^-11