Question

The weight of a proton is 1.64×10−26 N.  The charge on a proton is
+1.60×10−19 C.  If a proton is placed in a uniform electric field so that the electric
force on the proton just balances its weight , what is the magnitude and direction of
the field?
weight = E q

Answer 1

so...according to the question:

    mg = F

   mg = qE                   .........( F= qE)

 E = mg/q

 E = 10 -7 N/C