PHYA5 ~ 20th June 2013 ~ A2 Physics

R is the radius, r0 is a constant.

For the first one, did they give you the mass of a gold nucleus? If not, you'd have to work out the mas yourself by adding up proton and neutron masses, then dividing that by 4/3pi r^3.

(Mass comes to around 3.27x10^-25)

Okay so find the value of ro which is a constant so is the same for all nuclides.
For the next part us the equation density = mass/volume where the volume is the volume of a sphere and the value of r will be the constant you found out i part a).So it is safe to say that the density of thh nucleus is constant and independent of it's radius.So what i am trying to say is that R is the radius of the specific nuclide and r0 is a constant value same for all nuclides.
Hope this makes sense
Smith

How comes too many neutrons would cause a nucleus to be unstable?

I thought neutrons were supposed to be the 'glue' that helps hold everything together, like, they don't have the electrostatic repulsive force, but they do attract protons and neutrons together through the strong nuclear force. So it seems to me as though they could only act to increase stability inside the nucleus.

How comes too many neutrons would cause a nucleus to be unstable?

I thought neutrons were supposed to be the 'glue' that helps hold everything together, like, they don't have the electrostatic repulsive force, but they do attract protons and neutrons together through the strong nuclear force. So it seems to me as though they could only act to increase stability inside the nucleus.

With questions where you have to sketch these NZ graphs, is it exactly like how its in the book or do you use single lines?

Posted from TSR Mobile

I get confused when doing these .
I have no idea what the answer is but that's what I got. Help
Posted from TSR Mobile

I get confused when doing these .
I have no idea what the answer is but that's what I got. Help
Posted from TSR Mobile

I'm guessing you just multiplied 30 by root(10)? That is the way to go about it, but if you're not sure, think of it like this

I = k/r^2

so Ir^2 = k

then you can use that value of k, and the given value of intensity, to work out r^2 next time

I hate the light topic. I hate huguan

Posted from TSR Mobile

Essentially, the nucleus needs a specific amount of energy to be supplied to it to undergo fission. If this energy is supplied to it, then the nucleons have sufficient energy to work against the strong force, and the nucleus can split into two roughly equal fragments.

Remember that binding an additional nucleon into a nucleus *releases* energy, in the same way the energy is released when a nucleus is formed. For fissile isotopes like U-235, the energy that's released by binding this additional neutron into the nucleus is enough to cause it to split apart. If there was a way of just making another neutron appear, you're right, I imagine that it would contribute to stability if anything by increasing the strong force - but it's the fact that the energy released when it's binding to the nucleus overcomes the strong force that causes fission.

It's explained why this happens for some isotopes and not others here: http://en.wikipedia.org/wiki/Nuclear_fission#Input

the excess neutrons are not what makes the nucleus unstable. It is because of the excess protons. There is simply far too much electrostatic repulsion that even having more neutrons wont make it stable.

On question four for the applied paper june 2012 I don't understand the indicated power question. There is a mysterious 0.5 multiplied to the area under P-v diagram, number of cycles per second and number of cylinders. Can anyone explain this?

http://filestore.aqa.org.uk/subjects/AQA-PHYA52C-W-MS-JUN12.PDF

http://filestore.aqa.org.uk/subjects/AQA-PHYA5-2C-QP-JUN12.PDF

That makes sense, but some nucleus just decay due to having excess neutrons, rather than as a result of having just absorbed a neutron

i.e., they've had these neutrons for a long time, its not like they've just suddenly become unstable as a result of the energy released from absorbing a neutron

how do you explain beta minus decay? (where the neutron changes into a proton, this isn't fission, right?)

But there are nucleuses (nuclei?) that decay as a result of having too many neutrons, that is the actual cause, it says it in the textbook. This is what happens in a beta minus decay, a neutron changing into a proton.