Missing detail in the text:
"<span>A small glass bead has been charged to + 25 nC "
Solution
The force exerted on a charge q by an electric field E is given by
</span>
<span>Considering the charge on the bead as a single point charge, the electric field generated by it is
</span>
with
,
is the charge on the bead. We want to calculate the field at
:
The proton has a charge of
, therefore the force exerted on it is
And finally, we can use Newton's second law to calculate the acceleration of the proton. Given the proton mass,
, we have
The charge on the bead is positive, and the proton charge is positive as well, therefore the proton is pushed away from the bead, so: