OCR Physics G485 - June 2013 Unit 5 (OFFICIAL THREAD)

I only got the mark scheme. :<

Can anyone give me a model answer for the evolution of the universe ? Would be ever so grateful

v=(hubble constant)*x
45000000/ (65000/(1x10^6*3.1x10^16) = x
x = 2.15x10^25 m

Thats what I got.

Thanks, where did you get that from ? The long answer questions are the worst just can't seem to nail them.

so which one is hubbles constant?

Is this correct for when a star dies;
The outer layers expand and the star becomes a red giant. Then the core shrinks and collapses and becomes a white dwarf?

Use Hubble's law to work it out. V = Ho d where Ho = Hubble's constant. Speed of recession = 4.5x10^7 m/s
So,

distance = (4.5x10^7)/65x10^3 = 692.3 Mpc
1 Mpc = 10^6 x 3.1x10^16 = 3.1x10^22 m

Final distance in meters = 692.3 x 3.1x10^22 = 2.15x10^25 meters

so to find the distance you have divided the speed by the hubbles constant? but bubbles constant is 65kms^-1 mpc^-1? you divided it by 65000?

so to find the distance you have divided the speed by the hubbles constant? but hubbles constant is 65kms^-1 mpc^-1? you divided it by 65000? where has the mpc^-1 gone?

When the star starts to run out of hydrogen to fuse, gravity overcomes radiation pressure. The star starts to collapse which increases the pressure in the hydrogen shells around the core so they start fusing again. This increased radiation pressure causes the outer layers to expand into a red giant. The core continues to collapse, with stars < Chandrasekhar limit (1.3 solar masses) helium shell around the core fuses very quickly, the energy from this process blows off the outer shells leaving behind a white dwarf.
Edit: The white dwarf stops collapsing due to the electron degeneracy pressure (Fermi pressure) acting against gravity.

What do we need to know about nuclear waste?

What do we need to know about nuclear waste?

For capacitors in series: the charge Q is the same across both capacitors (as effectively they are a single capacitor with a large plate separation). The PD is split between the capacitors according to their capacitance. So work out the charge of the capacitors first using Q=VC for the whole circuit, then work out the PD across a single capacitor by using V=Q/C for one capacitor.

For resistors in series, current I is the same for all the resistors, and PD is split according to resistance. So work out I for the whole circuit with I=V/R and then work out V for one resistor with V=IR.

In parallel, V is the same for resistors and capacitors as they are effectively all connected in series to the battery so there is the same PD across them all.

Hooe this helps!

So hydrogen runs out.
Gravitational pressure overcomes radiation pressure.
Star collapses increasing pressure so fusion starts again (but I thought the problem was that the hydrogen had run out and not that the pressure was decreasing).
Increased pressure causes outer layers to expand and surface area cools, forming a red giant.
When the core collapses, does the red giant disappear?
And the bit after the red giant up till the energy blowing off, I haven't learnt this. :s
I basically just know that the core collapses and becomes a white dwarf.
Do you think I'll need to learn about the chandrasekhar limit and Fermi pressure? ):

What do we need to know about nuclear waste?

Use Hubble's law to work it out. V = Ho d where Ho = Hubble's constant. Speed of recession = 4.5x10^7 m/s
So,

distance = (4.5x10^7)/65x10^3 = 692.3 Mpc
1 Mpc = 10^6 x 3.1x10^16 = 3.1x10^22 m

Final distance in meters = 692.3 x 3.1x10^22 = 2.15x10^25 meters

I need to know the function of a.c generator in short so I can memorise.