The ideal mechanical advantage of the pulley system is 3
Answer :
Velocity will be 
Explanation:
We have given glass surface has a diameter of 1.5 mm
And charge q = 1.60 nC
Radius of electrons orbit r = height of electron above surface + radius of sphere = 
Force on electron is given by
, here q is charge on sphere and e is charge on electron

This force work as centripetal force
So 

v = 
The list of choices you provided with your question
is utterly devoid of any such examples.
Hello there!
Essentially, a control variable is what is kept the same throughout the experiment, and it is not of primary concern in the experimental outcome. Any change in a control variable in an experiment would invalidate the correlation of dependent variables (DV) to the independent variable (IV), thus skewing the results.