Decreasing the mass of a particle going through a Velocity Selector

[Hereformore]

Homework Statement

In a velocity selector, which of the following will lead to an increase in the exiting particle.

Homework Equations

Fb= qvB

Fe=qE

To travel straight the v = E/B

The Attempt at a Solution

I understand how varying E or B can change the velocity of the particle.

since only when Fb = Fe will the particle travel straight through, qvB=qE and so v =E/B.

But what I don't understand is why decreasing the mass wouldn't change the speed either.
Decreasing the mass would cause the particle to undergo a greater acceleration (same force, smaller mass), so the speed of the particle should be greater.

But the book I am using says it would not affect the exit speed. Trying to understand why. The forces are the same, since magnetic force and electric field force doesn't depend on mass. So the net force should be the same. If changing mass doesn't affect any of the component forces, then the net force should be the same in which case the acceleraiton should be higher with decreased mass. But apparently it doesn't change the exit speed of the particle?

Update: OH is it because there is no net acceleration in the horizontal direction, so changing the mass wouldn't change the horizontal exit speed?

 

[collinsmark]

Update: OH is it because there is no net acceleration in the horizontal direction, so changing the mass wouldn't change the horizontal exit speed?

I think you're on to something!

What does Isaac Newton's second law of motion say about the acceleration of a particle if the net force on that particle is zero? And does that result vary with the particle's mass?