e-fields line and COM

Purechick1989 SG

1) why e-field lines from a positive charged sphere are always drawn perpendicular to the surface of a metal plate? why e-field lines emerging from a charged sphere are also perpendicular to the surface?

2) when both objects collide and lose KE, is momentum still conserved? how do i explain it using N3L?

eagle SG

1) It's by convention... More of the direction of the forces that a charged particle will experience at that particular point in the E-field...

2) Momentum is still conserved. Have a look at the principle of conversation of momentum. Momentum is conserved as long as no external forces act on the system. N3L merely tells us that the force is equal but opposite within the system; the forces are all internal.

Chunhow SG

Hi, regarding your first question:

The electric fields coming out of a charged point particle or charged sphere can be resolved in two directions, as they are vectors. Perpendicular to surface, and tangential to surface. It is analogous to how projectile motion can be analyzed with respect to a X, and a Y direction.

The component in the tangential direction must be zero because there cannot be a force between two equipotential points. Therefore the electric field must be perpendicular..

I hope I'm right!