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



No. The gravitational force is doing work against the electric field. (In the absence of gravity the charge would move the other way.) Does the electrical PE increase or decrease?

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