Two engineering students, John with a mass of 86 kg and Marywith a mass of 59 kg

Question

Two engineering students, John with a mass of 86 kg and Marywith a mass of 59 kg, are 52 m apart. Suppose each has a 0.01%imbalance in the amount of positive and negative charge, onestudent being positive and the other negative. Find anapproximation of the electrostatic force of attraction between themby replacing each student with a sphere of water having the samemass as the student. Could someone help me out with this please? Thanks Two engineering students, John with a mass of 86 kg and Marywith a mass of 59 kg, are 52 m apart. Suppose each has a 0.01%imbalance in the amount of positive and negative charge, onestudent being positive and the other negative. Find anapproximation of the electrostatic force of attraction between themby replacing each student with a sphere of water having the samemass as the student. Could someone help me out with this please? Thanks

Explanation / Answer

first find the number of water molecules for each person. Youknow that there are one mole of molecules per .        1 + 1 + 16 =   18   grams    for water,so... .     86000 grams * 1 mole / 18 grams *   6.022 x 1023 molecules / 1 mole =   2.8772 x 1027 molecules . For Mary,   59 kg  gives      1.9739 x 1027 molecules . Each water molecule has 10 protons and ten electrons(one for each hydrogen, eight for each oxygen) so there are .        2.8772 x1028     and   1.9739 x 1028      positive andnegative charges for each person . There is a 0.01% "imbalance", which simply means that eachperson is missing this percentage of either the positive or thenegative charge. This percentage is the same as  0.0001   or    10-4  so . charge imbalance for the two people =     2.8772 x 1024electrons   and   1.9739 x1024 electrons . The net charge on each person can then be found by multiplyingthese numbers by the charge of one electron: .        John's charge =   2.8772 x 1024 * 1.60 x10-19 = 460352 Coulomb .        Mary's charge= 1.9739 x 1024 * 1.60 x 10-19 = 315824 Coulomb . Finally, the force between them =  k q for john * q for mary / r2 = .         = 8.99 x109 * 460352 * 315824 /522   =     4.83 x1017 Newtons     .       .      

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