How much work is required to bring three protons, initially infinitely far apart, to a configuration where each proton is 1.5×10−15m from the other two? (this is a typical separation for protons in a nucleus.) express your answer using two significant figures.

Explanation:

The work done(W) in bringing 2 protons to a separation 'r' is given as:

where,

k= coulomb's constant = 9 × 10⁹ N

q = charge of protons = 1.6 × 10⁻¹⁹ C

Now, the third charge (or proton) is brought near the other two  protons

Thus, work done against both these is

Now,

The total work done (W) =

or

or

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.