Question

A proton traveling at a speed 1.0*106 m/s of enters the gap between the plates of a 2.0-cm-wide parallel-plate capacitor. The surface charge densities on the plates are 1*10^-6 C/m2.

How far has the proton been deflected when it reaches the far edge of the capacitor? Assume the electric field is uniform inside the capacitor and zero outside.

I know the formula is E=symbol eta/epsilon for a parallel plate. But I don't what to do or how to start this.

Answer 1

Knowing E, you then know the force on the proton. From the velocity, you know the time the proton is in the plates (2cm wide).

F*time=massproton*velocity change.
the original velocity in the direction of E is zero, so velcity change must be final velocity, or twice average velocity during the transit.

distancedeflected=avgvelocity*time
=velocitychange/2 * time

you take it from here.