AQA Physics PHYA5 - Thursday 18th June 2015 [Exam Discussion Thread]

Q4 (c). June 2011. Why is the temperature higher and not lower? MS doesn't make sense to me that much :/

hi, could someone help with core 2014 question 1b ii. I know its a simple question im just getting myself confused, just not sure how to deal with the neutrons either side, thanks!

http://filestore.aqa.org.uk/subjects/AQA-PHYA51-QP-JUN14.PDF

Anyone?

Q4 (c). June 2011. Why is the temperature higher and not lower? MS doesn't make sense to me that much :/

There are two ways to figure out the energy given off.

One way is to calculate the change in energy (mass defect) of both sides and see how much energy that converts to.

You cannot do this method in this case because you must account for the K.E (of the neutrons) as well as the masses of each side.

The other way to do it is find the change in binding energy of both sides.

Neutrons don't have a binding energy.

So charge has nothing to do with the fact that alpha is more ionising then Beta?

Isn't Alpha positive 2 charge, so more likely to attract the electrons out of the atom it collides with if we put aside momentum for now

But in june 14 you do it the first way ignoring the neutrons!?

No they do the second way, binding energy = [binding energy per nucleon x number of nucleons] for each side where neutrons have no binding energy?

Well I've just done it using mass finding the change in energy and ignoring neutrons and I got the correct answer

Does anyone mind showing me how this would look please?


Mark scheme doesn't have an image to check against

Well I've just done it using mass finding the change in energy and ignoring neutrons and I got the correct answer

You're thinking is right only when alpha particles are not emitted towards any atoms or molecules. So in that case when alpha particles attract electrons, the electrons also attract alpha particles as stated by Newton. So in this case what is important is that which one of the particles will resist motion so that the other particle is moved towards the other particle. Electrons are attracted towards the nucleus of the atom. If the targeted atom has less protons than alpha particles then you would be right as the electrostatic force of attraction of alpha particles would overcome the electrostatic force of attraction of the nucleus of the atom towards the electron( hydrogen for example).

But usually this is not the case. When we talk about alpha particles we usually mean that they are traveling at a particular speed. Even though alpha particles have 2e charge their total mass is almost 7000 times greater than the mass of an electron. You could, for example, have 20 electrons as a particle (note that you can't join 20 electrons as a particle but this is an example for our purposes), fired at an atom to measure their ionising power. According to your reasoning this 20e particle would definitely beat alpha particles but if you think about it their mass is still 7000 less than the alpha particles and their momentum would easily be changed as they have less mass.


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Edit: typing error

Ok thanks for the explanation!

How does that even work


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How does that even work


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The only think i can understand about those microscopes is that i cannot understand them lol


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No way that's Turning points...

p.s the teacher guide is 1000x better then any stupid textbook, you were right