Multiple choice question 17 of 2014 past paper (1 Viewer)

[kashkow]

hey guys,

can someone please help explain this answer to me?

17. The diagram shows an alpha particle and a proton, placed at equal distances from two large charged metal plates.

[Diagram – the Alpha particle has 2 neutrons and 2 protons and the proton is a single proton.]

Which of the following best describes the motion of the particles?
(A) Both particles move with the same acceleration.
(B) The alpha particle moves with half the acceleration of the proton.
(C) The alpha particle moves with twice the acceleration of the proton.
(D) The alpha particle moves with a quarter of the acceleration of the proton.

I guessed C but the answer is apparently B but I can't figure out why. My reasoning is if the charge is doubled the acceleration is doubled and from looking at the equations that is what it seems but apparently it isn't. Is this a question i'll learn about later on in the year? (I'm up to about midway through Ideas and Implementation and this seems like a question of that category but i'm not sure...)

Any help would be much appreciated!
Thanks

 

[anomalousdecay]

Alpha particle is roughly 4 times heavier than the proton.

Force on the alpha particle is twice the force compared to that on the proton as it has twice the charge.

However, F = ma, so the alpha particle accelerates at half the rate as the proton accelerates.

 

[anomalousdecay]

My reasoning is if the charge is doubled the acceleration is doubled and from looking at the equations that is what it seems but apparently it isn't.

This statement is false. The force on the alpha particle is doubled. This is different to acceleration.

 

[kashkow]

Alpha particle is roughly 4 times heavier than the proton.

Force on the alpha particle is twice the force compared to that on the proton as it has twice the charge.

However, F = ma, so the alpha particle accelerates at half the rate as the proton accelerates.

Awesome. thanks heaps!