Coulomb's Law?

Question

Nobel laureate Richard Feynman (1918-1988) once said that if two persons stood at arm's length from each other and each person had 1% more electrons than protons, the force of repulsion between them would be enough to lift a "weight" equal to that of the entire Earth. Carry out an order-of-magnitude calculation to substantiate this assertion.

the answer is ~10^26N, but i don't know how to get this number.

Answer 1

Good question!

Let try to figure it out.
We are mostly water (H2O)
An average person weighs about say 60kg (45-80 kg )
So we we are about 60kg of water 1water molecule has 18 atomic units ( 2 + 8=10 protons and 8 neutrons)
1 proton is about the same weight as neutron

The ratio of protons to total weight is = 10/18= .556 that means we have
mass of all protons = 60 x 10/18= 33.3 kg
While a mass of a proton is =1.6726 E-27 kilograms
Do you see where I'm headed?

Number of protons is =33.3 kg/1.6726 E-27=19.901 E+27

1%=19.901 E+25 protons
1 proton has 1.6022 E−19 C

Total charge

Q= 19.901 E+25 x 1.6022 E−19
Q= 3.1898 E+9 C

Now we are ready for Coulombs Law

F=kQ^2/R^2.
k=8.987 E+9 N·m^2/C^2

F= 8.987 E+9 (3.1898 E+9 )^2/(1)^2
F= 9.1443 E +28 N

Confirmed and even more (like 100-800 times)