Hao asked in 科學其他:科學 · 1 decade ago

Coulomb's Law

Nobel laureate Richard Feynman once said that if two persons stood at arm's

length from each other and each personhad 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.

1 Answer

Rating
  • 1 decade ago
    Favorite Answer

    Taking the following data:

    Mass of proton = 1.66 x 10-27 kg

    Electronic charge = 1.6 x 10-19 C

    Permittivity of free space = 8.85 x 10-12 F/m

    Now, suppose that each person weighs 70 kg, standing at a distance of 0.5 m apart, we have:

    Mass of each person contributed by protons = 35 kg (assume that 1 proton weighs equally as 1 neutron and the mass of electrons is negligible)

    No. of protons of each person = 35/(1.66 x 10-27) = 2.108 x 1028

    Proton charge = 2.108 x 1028 x 1.6 x 10-19 = 3.37 x 109 C

    Then, excessive elctronic charge = 3.37 x 109 x 0.01 = 3.37 x 107 C

    So the repulsive force between the persons is:

    (3.37 x 107)2/(4π x 8.85 x 10-12 x 0.52) = 4.09 x 1025 N

    which is about 4.17 x 1024 kg, of the order of the mass of the earth (5.98 x 1024 kg)

    Source(s): Myself
Still have questions? Get your answers by asking now.