Question
1.3: Check
that the ratio ke2/G memp is
dimensionless. Look up a Table of Physical Constants and determine the value of
this ratio. What does the ratio signify?
Answer : The given ratio is 
.
.
Where,
G = Gravitational constant
Its unit is N m2 kg−2.
me and mp = Masses of
electron and proton.
Their unit is kg.
e = Electric
charge.
Its unit is C.
∈0 = Permittivity of free space .Its unit is N m2 C−2.
Hence, the given ratio is dimensionless.
e = 1.6 × 10−19 C
G = 6.67 × 10−11 N m2 kg-2
me= 9.1 × 10−31 kg
mp = 1.66 × 10−27 kg
Hence, the numerical value of the given ratio is
This is the ratio of electric force to the gravitational force between a
proton and an electron, keeping distance between them constant.
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