# Charged proton enters an electric field

Homework Statement:
A proton with horizontal velocity enters a region with a constant electric field of 1.0 x 10-7 N/C that points upwards (away from the Earth). Describe the trajectory of the proton
Relevant Equations:
(mp=1.67 x 10-27 kg, qp=e=1.6 x 10-19 C).
FE= E x q. Fg= mg
I tried to do Net force with electric field = E x q minus the gravitational force= mg. However, this gives me a negative net force suggesting the proton is moving downwards. I'm not sure this is correct as the initial velocity was horizontal. Was there no gravitational force before? Am I missing a step?

berkeman
Mentor
Homework Statement:: A proton with horizontal velocity enters a region with a constant electric field of 1.0 x 10-7 N/C that points upwards (away from the Earth). Describe the trajectory of the proton
Homework Equations:: (mp=1.67 x 10-27 kg, qp=e=1.6 x 10-19 C).
FE= E x q. Fg= mg

Net force with electric field = E x q minus the gravitational force= mg
The force due to the electric field does not involve a vector cross product. The force due to a magnetic field does involve a cross product. Or are you using "x" to represent a multiplication?

haruspex