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

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1. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
I thought the angle was 31 not 59. Because it went 30 up and 18 across..not the other way round.
2. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
My answers that i can remember

Acceleration was a vector quantity in the scalar section
Radius of satellite was 10m (2 sf)
For the slope question had mgsin(θ)=ma rearranging gets sinθ =a/g then a=2ms squared and g =9.8ms squared so θ=11.8 (3 sf)
magnitude of resultant force was 120N-90N (vertical component ) and horizontal component 18N, using Pythagoras got magnitude 35N (2 sf) and using inverse tan(30/18) got angle between resultant force and horizontal θ= 59.0
Velocity of horizontal component of projectile motion =24cos30
Velocity of vertical component of projectile motion =24sin30
Last question - Underwater turbines produce less noise pollution ? and absence of wind turbines makes environment aesthetically pleasing?
Satellite question - When both rockets are fired the satellite acts as a couple? there is rotation about a point but no linear acceleration ? and only when A is fired there is clockwise/anticlockwise motion not sure which way.
X is brittle where once the material exceeds its elastic limit it breaks. The material obeys hooke's law. The ultimate tensile strength of the material is where material breaks.
Y- Does not obey Hooke's law. When the force is removed the material returns to its original dimensions.
3. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
(Original post by emah123)
the other anglle question was for the vector triangle and i got 45 degrees, i thought that was right but people are saying it was 53 or something,

what did other people get for the angle?
I go 59
4. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
I found this paper was much more heavily weighted on the stress strain side of the topic and less on kinematics which was annoying, but lots of easy definition questions.

What did people put for the two last written questions about the more power produced by a sea turbine with the same speed and a wind turbine etc..?
5. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
Why did you have to find the angle from the horizontal?
6. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
What did everybody get on the 3rd last question, 'work out the radius of the turbines?'
I done a simultaneous equation between the actual volume of the cylinder and pieXr^2Xh, but got stuck on finding H and completely flopped it
7. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
In the question they asked from the horizontal if i can recall correctly xd
8. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
(Original post by Speedo)
What did everybody get on the 3rd last question, 'work out the radius of the turbines?'
I done a simultaneous equation between the actual volume of the cylinder and pieXr^2Xh, but got stuck on finding H and completely flopped it
Yeah I messed it up too, but h was 3m, since water went at a speed of 3ms^-1
9. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
(Original post by Speedo)
What did everybody get on the 3rd last question, 'work out the radius of the turbines?'
I done a simultaneous equation between the actual volume of the cylinder and pieXr^2Xh, but got stuck on finding H and completely flopped it
I tried to do that too except i first found the volume and then subbed it into the volume of a cylinder equation (pi r^2h) but then realised i had two unknowns: the radius and h and I wasn't quite sure how to find h I got it to be 3m but then i had a radius smaller than a metre?? . hopefully pick up method marks though
Last edited by imogen--; 17-05-2012 at 11:43.
10. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
Satellite question

height =3m= speed of sea water(3m/s) passing through multiplied by the time taken(1s)

Equate mass/volume=density equation to volume of cylinder. mass is known and density known so volume can be calculated. Volume divide by the height of 3m and by pi. Square root answer to get radius of 10m (2 sfs) xd
11. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
What did people get for the calculation questions on like power I think..? Not sure about those though they're probably supposed to be easy..
12. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
(Original post by Butterkist123)
I thought the angle was 31 not 59. Because it went 30 up and 18 across..not the other way round.
i got 59 as well
13. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
u know for the satellite q.. if i put the it moves to the right as the force is exerted to the left.. will i get no marks? coz ppl said is abt moment... clockwise moverment -o-
14. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
Power=2.6W (J/s) i got
15. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
Power=2.6W (J/s) i got
Yes so happy, took me quite a bit of working, but I got 2.6 as well.

Damn, that 5 mark deforming solids qualitative question took the absolute p***.
16. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
Standard paper, standard grade boundaries IMO probably around 43/44 for an A, I made a few stupid mistakes (ah well nothing I can do about it now) but I reckon I have around 54/53 and around 51 at worst so definate A for me I'm pretty happy about it just need to get a decent mark on WEP to secure the A overall.
17. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
(Original post by imogen--)
I found this paper was much more heavily weighted on the stress strain side of the topic and less on kinematics which was annoying, but lots of easy definition questions.

What did people put for the two last written questions about the more power produced by a sea turbine with the same speed and a wind turbine etc..?
I said that water is denser than air, so more mass passes through the turbine per second; KE = 0.5mv^2 so this means more energy per second, which means more power. For the last part about another advantage I just put that they are not easily visible so less likely to encounter opposition because of their ugliness
18. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
(Original post by stackemup)
Yes so happy, took me quite a bit of working, but I got 2.6 as well.

Damn, that 5 mark deforming solids qualitative question took the absolute p***.
Did you work use SUVAT to work out displacement? Then put that into work done is force x distance? Then divide by time?

That's what I did but I cant remember my answer :\

Also, what was the answer to the previous question. The one where you had to work out the force of the spring or something?
Last edited by Rough Silk; 17-05-2012 at 12:54.
19. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
so glad moments did make an appearance :L

what did everyone put for the motion of the satelitte when
-both rocket motors were switched on
-only rocket motor A was switched on

loads of my friends had different answers because "it was moving from left to right" !?
20. Re: OCR Physics A G481 Mechanics [Thursday 17th May 2012]
(Original post by stackemup)
Yes so happy, took me quite a bit of working, but I got 2.6 as well.

Damn, that 5 mark deforming solids qualitative question took the absolute p***.
Hi, could you possibly explain to me how you got 2.6? Please?
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