A pos charge can't experience a force perpendicular to a set of charged plates
yes it does. A positive charge is repelled by the positive plate, and attracted by the negative plate. Thus the force of the electric field between the places, is directed from the positive plate, to the negative plate, for any positive charge, and thus, the force on the positive charge is perpendicular to the charged plates.
maybe your getting electric field mixed up with magnetic? cause you mention that problem after talking about some school mucking up the forces by magnetic fields on charges.
A, a rocket out of fuel in deep space.. or
B, a projectile at it's max hieght.
personally i thought it was b, because theres no horizontal acceleration and vertically all forces cancel each other for an instant.
in the answers it was A.
A projectile only has one force acting on it, gravity. It has an initial force applied to it, by something, but once the projectile has lost contact with it (unless its something like a magnetic gun) then the only force acting on it is gravity. Thus it is accelerating. Though its velocity may be zero at that point in time (max height) it still has acceleration due to gravity, and thus, is still in an accelerated frame of reference.
Whilst its true that any space object has a gravitation field acting upon it (whether it be the galaxy, a planet), since a gravitational field is taken to be infinite, no matter how strong it is, out in deep space, the acceleration is minute. Thus, the acceleration due to gravity, can be taken as zero, since its so small. (deep space meaning that its far away from major gravitational fields/influences). Taking that point of view, the rocket in deep space is in an inertial frame of reference, since the forces acting on it are insignificant. If left there for millions of years perhaps, it would be attracted to some other space object, and there would be a significant amount of force for it to be undergo significant acceleration, but we're not looking at such pedantics.
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