# PHYA5 ~ 20th June 2013 ~ A2 Physics Watch

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#1621

(Original post by

de Broglie one .... 4 marker. I thought it was pretty sneaky

did anyone convert the eV into V by multiply eV by e

then multiplying it by e again to get eV

I thought it was sneaky as hell

**posthumus**)de Broglie one .... 4 marker. I thought it was pretty sneaky

did anyone convert the eV into V by multiply eV by e

then multiplying it by e again to get eV

I thought it was sneaky as hell

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#1622

**posthumus**)

de Broglie one .... 4 marker. I thought it was pretty sneaky

did anyone convert the eV into V by multiply eV by e

then multiplying it by e again to get eV

I thought it was sneaky as hell

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#1623

(Original post by

You did? Didn't the question say it was known to be 0.50m and you had to show it?

**#Bi-Winning**)You did? Didn't the question say it was known to be 0.50m and you had to show it?

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#1624

(Original post by

I only multiplied it by e once because an electron volt is voltage, so you multiply it by charge to get energy

**The H**)I only multiplied it by e once because an electron volt is voltage, so you multiply it by charge to get energy

But e x V would give you energy

but they gave you eV... it looks like they've given you kinetic energy already which was so misleading

was a 4 marker, that's the one I didn't have a good feeling about

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#1625

by the way anyone know for astrophysics i got the resolving angle wrong for the radio wave, but for the show that were we meant to multiply the radius of the event horizon by 2?

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#1626

(Original post by

Yeah same i got 2.5x10-19, but i didnt write that done cos i thought it was wrong i still wrote the method out, will i get a few marks?

**Jam Jam24**)Yeah same i got 2.5x10-19, but i didnt write that done cos i thought it was wrong i still wrote the method out, will i get a few marks?

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#1628

(Original post by

Hmmm not sure

But e x V would give you energy

but they gave you eV... it looks like they've given you kinetic energy already which was so misleading

was a 4 marker, that's the one I didn't have a good feeling about

**posthumus**)Hmmm not sure

But e x V would give you energy

but they gave you eV... it looks like they've given you kinetic energy already which was so misleading

was a 4 marker, that's the one I didn't have a good feeling about

As a unit, eV is electron volt so it must be multiplied by charge to make it J

As an equation eV is the total energy, like eV = 1/2mv^2

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#1629

(Original post by

Attachment 228434

The formation of Helium gives off much more energy per nucleon than a normal fission. It's just over 7MeV per nucleon and there are 4 nucleons so that's 20-something MeV

**SpiggyTopes**)Attachment 228434

The formation of Helium gives off much more energy per nucleon than a normal fission. It's just over 7MeV per nucleon and there are 4 nucleons so that's 20-something MeV

http://en.wikipedia.org/wiki/Nuclear_fission#Output

says that it's 200MeV

this isn't even the question so it doesn't really matter

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#1631

(Original post by

What was the answer for mass at -50degrees.

**sports_crazy**)What was the answer for mass at -50degrees.

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#1632

(Original post by

I agree that that's around the answer for the question, but you're still missing the point fission reactions produce more energy than fusion reactions. I understand that there is a greater change in binding energy, and hence more energy released PER NUCLEON, but since there are so many more nucleons in fission, it outputs more energy. Even though the change in binding energy is only around 1Mev per nucleon, there are around 200 nucleons involved, so it's much more

http://en.wikipedia.org/wiki/Nuclear_fission#Output

says that it's 200MeV

this isn't even the question so it doesn't really matter

**bugsuper**)I agree that that's around the answer for the question, but you're still missing the point fission reactions produce more energy than fusion reactions. I understand that there is a greater change in binding energy, and hence more energy released PER NUCLEON, but since there are so many more nucleons in fission, it outputs more energy. Even though the change in binding energy is only around 1Mev per nucleon, there are around 200 nucleons involved, so it's much more

http://en.wikipedia.org/wiki/Nuclear_fission#Output

says that it's 200MeV

this isn't even the question so it doesn't really matter

What section is this?

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#1633

**Core Questions**

__Question 1__

a) Definition of atomic mass unit = 1/12th of the mass of Carbon-12 atom

b) Why do stars need a high temperature for fusion to occur?

- Fusion is when two smaller nuclei combine

- This occurs when the electrostatic force of repulsion is overcome

- Since Temperature is proportional to kinetic energy, a high temperature gives the nuclei enough energy to overcome the electrostatic force

c) Fill in the gaps : Positron emission

d) Energy released = 24.7 MeV (can't remember)

__Question 2__

a) How do you decrease power output?

- By lowering the control rods

- which absorb the neutrons

- and therefore lower the rate of fission reactions

b) What is the source of the nuclear waste?

- used fuel rods

- fission fragments are highly unstable (usually neutron rich)

c) Describe and explain the radiation emitted by the moderator...

- electrons in the nucleus are excited

- when the electrons de-excite, photons of discrete wavelengths are produced

- these photons have a high frequency and high energy (E=hf)

- they are therefore gamma photons

__Question 3__

a) Temperature change = 8.5... Degrees Celsius

b)

c) Mass of ice = 0.16kg (exact values) 0.15kg (8 degrees Celsius used)

__Question 4__

a) What is an ideal gas?

- a gas that obeys Boyle's Law

- i.e. pV = constant at constant temperature

b) Number of moles

- 130 moles

c) Density

- 26 kgm^-3

d) Mass of gas left in cylinder

- Can't remember

__Question 5__

Discuss how you can determine what radiation is produced by the source using different absorbers. Discuss the safety precautions, what you would measure and what conclusions you can make

*Please add to this*

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#1634

**bugsuper**)

I agree that that's around the answer for the question, but you're still missing the point fission reactions produce more energy than fusion reactions. I understand that there is a greater change in binding energy, and hence more energy released PER NUCLEON, but since there are so many more nucleons in fission, it outputs more energy. Even though the change in binding energy is only around 1Mev per nucleon, there are around 200 nucleons involved, so it's much more

http://en.wikipedia.org/wiki/Nuclear_fission#Output

says that it's 200MeV

this isn't even the question so it doesn't really matter

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#1635

(Original post by

What section is this?

**wy95**)What section is this?

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#1636

(Original post by

What was the answer for mass at -50degrees.

**sports_crazy**)What was the answer for mass at -50degrees.

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#1637

(Original post by

That's the problem in some cases, confusion between the equation eV and the unit eV

As a unit, eV is electron volt so it must be multiplied by charge to make it J

As an equation eV is the total energy, like eV = 1/2mv^2

**The H**)That's the problem in some cases, confusion between the equation eV and the unit eV

As a unit, eV is electron volt so it must be multiplied by charge to make it J

As an equation eV is the total energy, like eV = 1/2mv^2

I'm pretty sure regardless we have both got 2 marks at least

I hope grade boundaries are low - by the sounds of it here, people found it quite easy.... my class found it tough though

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#1638

(Original post by

Oh well, lets not worry too much about it now

I'm pretty sure regardless we have both got 2 marks at least

I hope grade boundaries are low - by the sounds of it here, people found it quite easy.... my class found it tough though

**posthumus**)Oh well, lets not worry too much about it now

I'm pretty sure regardless we have both got 2 marks at least

I hope grade boundaries are low - by the sounds of it here, people found it quite easy.... my class found it tough though

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#1639

(Original post by

fusion releases more energy than fission?

**Acruzen**)fusion releases more energy than fission?

because even though the change in binding energy for each nucleon is less there are more nucleons involved

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#1640

**bugsuper**)

I agree that that's around the answer for the question, but you're still missing the point fission reactions produce more energy than fusion reactions. I understand that there is a greater change in binding energy, and hence more energy released PER NUCLEON, but since there are so many more nucleons in fission, it outputs more energy. Even though the change in binding energy is only around 1Mev per nucleon, there are around 200 nucleons involved, so it's much more

http://en.wikipedia.org/wiki/Nuclear_fission#Output

says that it's 200MeV

this isn't even the question so it doesn't really matter

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