Note that in this example we have ignored the acceleration
due to gravity in calculating the time of fall To see if this is justified,
let us calculate the acceleration of the proton in the given electric
field:
p
p
e E
a
m
=
     
19
4
1
27
(1 6
10
C)
(2 0
10
N C
)
1 67
10
kg −
−
−
×
×
×
=
×
     
12
–2
1 9
10
m s =
×
which is enormous compared to the value of g (9