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Question: Two identical blocks are placed 5 m apart. Each has a mass of 5 kg, is electrically neutral, and ...

Two identical blocks are placed 5 m apart. Each has a mass of 5 kg, is electrically neutral, and is made entirely of copper.
Note: One copper atom has a mass of 1.055·10-25 kg and contains 29 protons.

c.) Estimate how many electrons each of these blocks has within it.

What is the total charge of all these electrons?

And what is the total charge of all the protons in a block?

d.) You now remove an equal amount of electrons from each block, so the electric repulsion of the blocks cancels their gravitational attraction to each other.
(Note: You may assume the mass of the blocks is not significantly reduced when removing these electrons-- why?)

What is the net charge of each block now?

How many electrons were removed from each block? Give a number, and then also express this as a percentage of the total number in the block.

) Suppose ALL of the electrons suddenly disappeared from the blocks. How much repulsive force would the blocks exert on each other (initially, before each block itself dispersed)? Express in Newtons and as multiples of the weight of a jetliner (about 106 N).

Explanation / Answer

One copper atom has a mass of 1.055·10-25 Kg and contains 29 protons.

so let us first calculate the number of copper atom in 5kg

5Kg Block will have 4.93 x 1025 copper atom

Each atom has 29 protons and 29 electrons(as the atom is neutral)

So total no. of electron/proton =142 x 10 25

Total charge can be calculated by multiplying the total number with charge of each electron/proton

Total charge will be 228.75 x 106 Columbs Because of electrons and protons separately

NET TOTAL CHARGE ON BLOCK IS ZERO AS IT IS NEUTRAL

setting the gravitational force of attraction equal to the electric (force of repulsion),

F_g = F_e
G * M^2 / r^2 = k * Q^2 / r^2
Since r is the same in both equations, we can cancel it out, leaving us with,
G * M^2 = k * Q^2
Now we want to solve for Q,
Q^2 = G * M^2 / k
Q = sqrt (G * M^2 / k)

Checking the units on this equation we can confirm that the answer does, in fact, have units of Coulombs (which is the unit of electric charge).

Remembering what all those letters stands for,
G = 6.67 E-11 N m^2 * kg^-2
M = 5 kg
k = 8.99 E9 N m^2 / C^2

Plugging into the equation we just solved for,
We get,
Q = 1.85 X10-19 Coulombs

Number of electron removed =Q/e=1.156electron

Now if all the electrons removed only protons will be left and their force can be calculated using coloumbs law.

Last part is not clear please edit the question so that i can update the answer

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