11-71. A particular proton in space is subjected to two fields: a gravitational field (1.30X105 N/kg  toward planet X), and an electric field (2.47X10-4 N/C away from planet X).
 (a) If the proton is released from rest, in which direction will it move?
 (b) After moving 1.50 m, what will be its speed? Use energy methods and assume uniform fields.


ACCUMULATED SOLUTION

FE = qE     Fg =  mg
The mass of the proton is 1.673X10-27 kg and the charge on a proton is 1.602X10-19 C


Fg =  mg = (1.673X10-27 )(1.3X105) = 2.175X10-22 N
FE = qE = (1.602X10-19 )(2.47X10-4) = 3.957X10-23 N

The proton moves
(A)   toward the planet
(B)   away from the planet