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OCR Physics A G481 Mechanics [Thursday 17th May 2012]

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Original post by Mattyd951
Don't know why everyone got 2.6W for the spring one... I got 1.3W and I think (hope) that was right!
The others I can remember were:

11.8 degrees for the slope
10m radius for the turbine
27.3% efficient for turbine
119Kg mass of the rider
7.33m height of the ball
59 degrees for the balloon angle


From what I can remember I got all of those too, I thought that it was a fairly easy paper actually! Would love to see an unofficial mark scheme though.. I hope someone can get hold of the paper soon :smile:
Reply 141
how much is the Power question scored?
Less Kinematics than I was hoping for. Lots of easy questions and quite a few hard questions, not much in the middle. I reckon it will be a high grade to pass (+-50%) and a low grade to get an A. Maybe 42/43.
I left most of my answers to 2 s.f., will I lose marks? For instance, I left the mass as 120kg, the power as 1.3W, the percentage efficiency as 27% etc.

Think I'll lose marks?

:s-smilie:
Reply 144
Original post by Mattyd951
Don't know why everyone got 2.6W for the spring one... I got 1.3W and I think (hope) that was right!
The others I can remember were:

11.8 degrees for the slope
10m radius for the turbine
27.3% efficient for turbine
119Kg mass of the rider
7.33m height of the ball
59 degrees for the balloon angle


yeah same except got 2.6W which i think is wrong.
Original post by .Username.
Does anyone reckon they got 53+


Yes!
Reply 146
how much out of 60 should i get if i want 80/90 in UMS score?
Reply 147
About the angle question... How did everyone get 53 degrees????

i thought net force up was 30
18 to the right
Tan= Opposite/ adjacent
So i did inverse tan (18/30) and got 31 degrees?
Reply 148
Original post by mack94
About the angle question... How did everyone get 53 degrees????

i thought net force up was 30
18 to the right
Tan= Opposite/ adjacent
So i did inverse tan (18/30) and got 31 degrees?


I did exactly the same as u did
Reply 149
Original post by Eric_lee
I did exactly the same as u did


I think it wanted the angle to the horizontal though :frown:
We worked out the angle the the verticle:mad:
Reply 150
One more question people as for the other angle question... How did everyone get 11.8??

W sin(angle) = ma
sin(angle) = a/g
Inverse sin (3/9.81) = 17.8 degrees :s-smilie:

Either my methods wrong or my acceleration which i calculated to be 3 ms-2 is wrong.
someone please help a brother out and tell me where i went wrong?
Reply 151
when can someone get hold of a paper and make a markscheme?? i getting really paranoid now :s-smilie:
Original post by mack94
One more question people as for the other angle question... How did everyone get 11.8??

W sin(angle) = ma
sin(angle) = a/g
Inverse sin (3/9.81) = 17.8 degrees :s-smilie:

Either my methods wrong or my acceleration which i calculated to be 3 ms-2 is wrong.
someone please help a brother out and tell me where i went wrong?


The acceleration was 2.
Reply 153
Original post by mack94
One more question people as for the other angle question... How did everyone get 11.8??

W sin(angle) = ma
sin(angle) = a/g
Inverse sin (3/9.81) = 17.8 degrees :s-smilie:

Either my methods wrong or my acceleration which i calculated to be 3 ms-2 is wrong.
someone please help a brother out and tell me where i went wrong?




Acceleration is 2 ms^2
Reply 154
Original post by mack94
I think it wanted the angle to the horizontal though :frown:
We worked out the angle the the verticle:mad:


sorry , i got a mistake. i got 59 degree of the angle from aretan(30/18)
yayayayay! I got 7.3 m for the height of the ball as well! Gaaah, so happy- thought I had completely bummed that question, well that's 2 0r 3 out of 60... woooh
I despair. My academic life is over.Not really but yeah.I despair.

First question, I forgot to half the time so I got double the distance 14.7.How.Very.Idiotic.
Then for the angle I got 11.8...but misread the followup question and ended dividing the force 510 by sin11.8x9.81(I thought wsin11.8=510)...I had worked out that the acceleration had become -4.29 but I thought this was too simple and crossed it out =/..wth,my silly brain.

For the rockets when they are both fired, I said they remained in rotational equilibrium,at constant speed, no acceleration.sum of moments=0.
And when only a was fired, the satellite gained momentum, and rotated clockwise.

I need at least 85 Ums marks for it all to be an overall A.
Original post by Charlottek12
From what I can remember I got all of those too, I thought that it was a fairly easy paper actually! Would love to see an unofficial mark scheme though.. I hope someone can get hold of the paper soon :smile:


Aha, awesome! As long as someone else has got the same then it's all good! :smile:
Reply 158
I got all the way to finding the volume of of water, then to find the radius i used volume of a sphere by accident :frown:
Reply 159
wooh seeing these answers are making me feel better thought i did really bad... stupidly forgot stress and pressure had the same units pa though :frown:

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