In a quarter of an hour it will travel 1/4 x 90 = 22.5Km
Cause it reflects i think so
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 = 
Answer: People know that they jap e learned by their mistakes or by someone ya being them something