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1The proton because it has double the acceleration.

2The acceleration of the electron will increase. The time to reach the end of the plates will be the same and since s=1 2 a t 2 the distance will increase and so the electron will get closer to the plate.

3The average force is F¯=m Δ v Δ t. During half a revolution, Δv = 2v and Δ t=1 2×2 π m q B so that F¯=2 v q B π.

4The work done on the proton by the magnetic force is zero. But the work done is the change in kinetic energy. So the kinetic energy does not change and neither does speed.