Step 1: The magnitude of the electrostatic force between an electron and a proton is Fe=r2kqe2, and the gravitational force is Fg=r2Gmemp.
The ratio is
FgFe=Gmempkqe2
where k=9×109N⋅m2/C2, qe=1.6×10−19C, G=6.7×10−11N⋅m2/kg2, me=9.1×10−31kg, mp=1.67×10−27kg.
Step 2: Compute qe2:
qe2=(1.6×10−19)2=2.56×10−38C2.
Numerator: kqe2=9×109×2.56×10−38=23.04×10−29=2.304×10−28N⋅m2.
Step 3: Compute memp:
memp=9.1×10−31×1.67×10−27=15.197×10−58=1.52×10−57kg2.
Denominator: Gmemp=6.7×10−11×1.52×10−57=10.184×10−68=1.02×10−67N⋅m2.
Step 4: Compute the ratio:
FgFe=1.02×10−672.304×10−28=1.022.304×10−28−(−67)=2.26×1039≈2.3×1039.
(b) 2.3×1039
(b)