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# 19/05/10 Edexcel Phy 6(6PH08) watch

1. First question: got average diameter 0.27 mm (excluding outlier), uncertainty 4%, density 8400 kg/m^3, nichrome.

Second question: use a metre rule with set squares to measure h. I put the time uncertainty as 0.5 sec because that's what they said in the specimen mark scheme, and got a huge uncertainty of 33% for the kinetic energy! Maybe they wanted a smaller reaction time this time What values did people get for the kinetic energy?

Third question: strange to have a cosmology question in a practical-type paper! I got the value of Hubble's constant from the graph as about 69 km/s/Mpc.

Fourth question: put pointing detector straight at source for accuracy precaution, holding source in tongs for safety, and variable to keep fixed was distance between detector and source. Did anyone draw a diagram for the first two parts?
2. (Original post by fredbraty)
what did you say on the "how do you think the astronomer will find the speed? "
Also how much did you find the percentage uncertainty of the kinetic energy?I found about 4-5%
At the astrophysics question the percentage difference i got was about 10%,large.
The gradient i got was 63-67 i cant remember...
Use red shift for the speed. I got 33% uncertainty for the KE, because of the reaction time business.
3. (Original post by wooper)
First question: got average diameter 0.27 mm (excluding outlier), uncertainty 4%, density 8400 kg/m^3, nichrome.

Second question: use a metre rule with set squares to measure h. I put the time uncertainty as 0.5 sec because that's what they said in the specimen mark scheme, and got a huge uncertainty of 33% for the kinetic energy! Maybe they wanted a smaller reaction time this time What values did people get for the kinetic energy?

Third question: strange to have a cosmology question in a practical-type paper! I got the value of Hubble's constant from the graph as about 69 km/s/Mpc.

Fourth question: put pointing detector straight at source for accuracy precaution, holding source in tongs for safety, and variable to keep fixed was distance between detector and source. Did anyone draw a diagram for the first two parts?
Hey wooper,

For the first question i agree with all you wrote but i dont remember if it asked for any uncertainties.
How much did you find the maximum mean speed ?
I think my value for the graph was about 67...But my percentage difference was quite high about 10%
I didnt draw a diagram since they didnt ask for it.For the safety,i wrote that he should wear a uniform and keep away from the source.Also the variable to remain constant is the distance between source and lead but also lead-dtetector..
4. (Original post by fredbraty)
what did you say on the "how do you think the astronomer will find the speed? "
Also how much did you find the percentage uncertainty of the kinetic energy?I found about 4-5%
At the astrophysics question the percentage difference i got was about 10%,large.
The gradient i got was 63-67 i cant remember...
Just as wooper said, use Doppler's shift (Red shift), z=v/c.

K.E. Uncertainty about 14-15%, cuz there was v squared, should double the uncertainty.. I used half range for uncertainty in time.

Didnt draw a diagram for radiation detection.. Nobody asked for that, huh? I expressed myself in words.
5. Has anyone got the paper?

fredbraty - I may have got a too-small value for the mean max velocity. Can't remember exactly.
Just as whooper said, use Doppler's shift (Red shift), z=v/c.

K.E. Uncertainty about 14-15%, cuz there was v squared, should double the uncertainty.. I used half range for uncertainty in time.

Didnt draw a diagram for radiation detection.. Nobody asked for that, huh? I expressed myself in words.
i used half range for the time too.
how much did you find the speed?
the kinetic energey was 0.16J i think...
how did you calculated the kinetic energy?i mean did you calculate the kinetic energy of each car separately or did you do 1/2x(m+M)xu^2 ?

sorry for my explosion :-p
7. (Original post by wooper)
Has anyone got the paper?

fredbraty - I may have got a too-small value for the mean max velocity. Can't remember exactly.
me too.0.58 m/s which is reasonable due to the low masses.
Do you think there will be an upgrade?
I want the A*
8. (Original post by fredbraty)
me too.0.58 m/s which is reasonable due to the low masses.
Do you think there will be an upgrade?
I want the A*
If velocity is less than 1 m/s, then kinetic energy should be less than 1J (mass was about 1 kg?). But using GPE and conservation of energy, we get mgh = 1 kg*10 m/s^2*1 m approximately, which is 10 J. What is going wrong here? Maybe we used the wrong units somewhere, e.g. mm instead of m?
9. did any of you have problems in plotting the last graph? edexcel said to avoid using scales of three in the TSM....that was the whole problem
10. (Original post by wooper)
If velocity is less than 1 m/s, then kinetic energy should be less than 1J (mass was about 1 kg?). But using GPE and conservation of energy, we get mgh = 1 kg*10 m/s^2*1 m approximately, which is 10 J. What is going wrong here? Maybe we used the wrong units somewhere, e.g. mm instead of m?
no the masses were in grams..the height was in mm,so reasonable
11. (Original post by kosy91)
did any of you have problems in plotting the last graph? edexcel said to avoid using scales of three in the TSM....that was the whole problem
yess i was reading that the last night so i didnt use scales of 3.i used scaled of 2.5.you?
12. (Original post by fredbraty)
Hey wooper,

For the first question i agree with all you wrote but i dont remember if it asked for any uncertainties.
How much did you find the maximum mean speed ?
I think my value for the graph was about 67...But my percentage difference was quite high about 10%
I didnt draw a diagram since they didnt ask for it.For the safety,i wrote that he should wear a uniform and keep away from the source.Also the variable to remain constant is the distance between source and lead but also lead-dtetector..
My mean maximum speed was 0.58 m.s-1 but, then i added (cause they wanted maximum) my uncertainty which was ((2x1*10-3 m) for height)+((0.26s) for the uncertainty of time in previous part, found it by using the range in table)
which became rounded to 0.88 m.s-1. Is that right?

I then got Kinetic energy to be 36 J.

%Uncertainty of K.E.= 2 x 0.262( which i found before)

then : (0.5/36) *100
and i got 1.45% rounded it to 1.5 %

For %P.D for the hubble constant, i got 63.333
then i did (( 71 - 63.333)/ avg of both)*100

I think i shoulve divided by 71 only
13. (Original post by fredbraty)
yess i was reading that the last night so i didnt use scales of 3.i used scaled of 2.5.you?
i started the scale from 5 for both the y and x axis. got gradient at 0.0425 mm-1
14. (Original post by Joann79)
My mean maximum speed was 0.58 m.s-1 but, then i added (cause they wanted maximum) my uncertainty which was ((2x1*10-3 m) for height)+((0.26s) for the uncertainty of time in previous part, found it by using the range in table)
which became rounded to 0.88 m.s-1. Is that right?

I then got Kinetic energy to be 36 J.

%Uncertainty of K.E.= 2 x 0.262( which i found before)

then : (0.5/36) *100
and i got 1.45% rounded it to 1.5 %

For %P.D for the hubble constant, i got 63.333
then i did (( 71 - 63.333)/ avg of both)*100

I think i shoulve divided by 71 only
yess they wanted maximum,but the formula they gave us was for the maximum speed.also, the points were few so it shouldnt require any other work.
How did you find the K.E that high?
yess you should divide by 71.dont worry though you wont lose a lot.
15. (Original post by Joann79)
My mean maximum speed was 0.58 m.s-1 but, then i added (cause they wanted maximum) my uncertainty which was ((2x1*10-3 m) for height)+((0.26s) for the uncertainty of time in previous part, found it by using the range in table)
which became rounded to 0.88 m.s-1. Is that right?

I then got Kinetic energy to be 36 J.

%Uncertainty of K.E.= 2 x 0.262( which i found before)

then : (0.5/36) *100
and i got 1.45% rounded it to 1.5 %

For %P.D for the hubble constant, i got 63.333
then i did (( 71 - 63.333)/ avg of both)*100

I think i shoulve divided by 71 only
hey....how you doing?

for the KE, I got a value of 0.16J. for the PD, I took the denominator as average as well. saw that somewhere the night before the exam.
16. (Original post by kosy91)
i started the scale from 5 for both the y and x axis. got gradient at 0.0425 mm-1
no on the x-axis i used a scale of 2.5.I started from 0 because there was a zero measurement on the table.My gradient was 0.0506...
17. (Original post by kosy91)
hey....how you doing?

for the KE, I got a value of 0.16J. for the PD, I took the denominator as average as well. saw that somewhere the night before the exam.
to do the average they should both be experimental,were they?i dont remember.
yess me too 0.16 J.
18. (Original post by fredbraty)
to do the average they should both be experimental,were they?i dont remember.
yess me too 0.16 J.
oh...i didnt know it had to be experimental. whichever book i have read, says you have to do average. ut why divide by 71 and not the gradient(64 or whatever)?
19. (Original post by kosy91)
oh...i didnt know it had to be experimental. whichever book i have read, says you have to do average. ut why divide by 71 and not the gradient(64 or whatever)?
the formula for the percentage difference=(actual-experimental)/actual *100%
when both values are experimental on the denominator we have (experimental1+experimental2)/2..oh well it shouldnt cost a lot.
20. (Original post by kosy91)
oh...i didnt know it had to be experimental. whichever book i have read, says you have to do average. ut why divide by 71 and not the gradient(64 or whatever)?
Im doing okey! What exam do you have next ??
I really got confused in the K.E question
How much do you think i'd lose marks over this
I guess its only supposed to be divided by 71 cause its the given value.

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