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# AQA June 2011 Mechanics 1B 26th May watch

1. (Original post by ezeffy)
I swear in the helicopter question it sed that the helicopter had stopped accelerating?
Don't remember seeing that, i remember the car on the motorway started decelerating, but can't remember anything about the helicopter stopping accelerating.
2. Heli didnt change acceleration at all.
(Original post by Joshp93)
The angle from which it hits the floor isnt dependent on the height or the distance it travelled i believe, instead its the two velocity components at the time it hits the floor which dictates its direction and hence the angle at which it hits the floor.
Would you not need height to work out the final velocity?
3. (Original post by seejay1)
Heli didnt change acceleration at all.

Would you not need height to work out the final velocity?
Well, the horizontal velocity doesnt change because there is no resitance force, and vertical velocity can be worked out by using v=u+at and you know t=4 and a=9.8 and u=0 so you can work out the vertical component to be 39.2 and the horiz is 250. so then the angle is tan(A)=39.2/250 which comes out to be 8.91 degrees
4. I am positive that the height was 78.4 m (0.5 x 16 x 9.8)
For the tension and the pully you have 5g - T = 5a and T-3g = 3a and as a was 2.45 that means that T is equal to 36.75 N...... i think i am right and not forgetting anything here.
For the projectile question, It hits the floor at an angle of 8.91 degrees from horizontal and as said by someone before, to find the the helicopter time you find the manitude of the acceleration and then substitute into r=ut+0.5at^2 knowing that r/s = 500.
For the last page you found two expressions in terms of P using the horizontal and vertical componants and then solve them silumtaneously by adding the two together to get an epression in terms of 2P and then divide by 2 to get it to 125 something.
5. Another thing on this paper that almost caught me out was the car on the motorway, when you had to draw the velocity/time graph i plotted my speed as 32ms-1 for the first 12.5s and then drew the line down to 18ms-1 until 64 seconds, although it should of been until 76.5s, just realising as i was checking my paper.
6. Sorry, I was being stupid xD forgot they gave us the time. Well the angle was worth more marks anyway
7. (Original post by hdiriaur)
I am positive that the height was 78.4 m (0.5 x 16 x 9.8)
For the tension and the pully you have 5g - T = 5a and T-3g = 3a and as a was 2.45 that means that T is equal to 36.75 N...... i think i am right and not forgetting anything here.
For the projectile question, It hits the floor at an angle of 8.11 degrees from horizontal and as said by someone before, to find the the helicopter time you find the manitude of the acceleration and then substitute into r=ut+0.5at^2 knowing that r/s = 500.
For the last page you found two expressions in terms of P using the horizontal and vertical componants and then solve them silumtaneously by adding the two together to get an epression in terms of 2P and then divide by 2 to get it to 125 something.
You got almost all the same as me except the tension, which i think i screwed up, but i got 8.91 not 8.11 for the degrees? was that a typo?
8. (Original post by seejay1)
Sorry, I was being stupid xD forgot they gave us the time. Well the angle was worth more marks anyway
Well atleast you werent being stupid in the exam and got the right height, i am begining to realise some slight simple mistakes ive made that may cost me about 5 or 6 points, ah well not to worry
9. Hey guys, can any of you recall what you got for the bearing in the helicopter question, I got 36.9 degrees, did anyone get the same ... also the angle on the projectiles question, i got 8.9 ... So worried i lost the marks, want to see if its correct .. thanks
10. (Original post by Joshp93)
You got almost all the same as me except the tension, which i think i screwed up, but i got 8.91 not 8.11 for the degrees? was that a typo?
yeah i got 8.91 as well i just made a mistake whilst typing. I suppose i might edit that....
11. (Original post by jj696)
Hey guys, can any of you recall what you got for the bearing in the helicopter question, I got 36.9 degrees, did anyone get the same ... also the angle on the projectiles question, i got 8.9 ... So worried i lost the marks, want to see if its correct .. thanks
8.9 degrees is right, but for my bearing i think i got 053 not entirely sure though, i think i worked out the angle and got 36.9 but then took it away from 90, since it was the other angle which was the bearing... cant remember exactly though
12. (Original post by jj696)
Hey guys, can any of you recall what you got for the bearing in the helicopter question, I got 36.9 degrees, did anyone get the same ... also the angle on the projectiles question, i got 8.9 ... So worried i lost the marks, want to see if its correct .. thanks
Bearing, so 90-037 degrees... or 37. 53 or 37 not sure!
13. (Original post by seejay1)
Bearing, so 037 degrees...
The bearing was 053 and 36.7 degrees was the angle between the horizontal and the direction so you then needed to minus it from 90..... i think.
14. (Original post by Joshp93)
For finding the tension in the string, with the two weights, did everyone get T=3g+5g=78.4N? im starting to think i may have messed up on that one, but its worth only 2 marks so not to bothered if i did.
I'm pretty sure I got 78.4N for the tension too.

The bearing was 053 and 36.7 degrees was the angle between the horizontal and the direction so you then needed to minus it from 90..... i think.
Yeah this sounds right to me.
15. (Original post by AlesanaWill)
I'm pretty sure I got 78.4N for the tension too.
Well atleast somebody did but im still not convinced it's right, and yea the bearing one i cant even remember any values i got, but im just going with your answer that you got 37 so that means the bearing must be 053, since its the angle from the verticle you want.
16. Ok Guys, here are my answers, i got bored during the exam cos i finished so i wrote my answers on some paper and kept it to put up here:
i just wrote answers to the questions, cant remember which sub question goes with which answer so soz but yh..

1) 0.2, 3, 8000
2) 39.2, 11.76, 4.56
3) 400, 64, 26.1
4) m = 9, v = 63 (i forgot to divide it by 9 lol so v is actually 7 )
5)2.45, 36.75, string is light & inextensible, 0.4, 0.98
6) 250, 78.4, 39.2, 253, 8.91 (degrees)
7) 10i+7.5j, 053 (degrees), 40
8) 1.73

i wanna say feel free to criticise if i got stuff wrong, but dont like.. destroy me with criticism
17. (Original post by Jabz.x)
Ok Guys, here are my answers, i got bored during the exam cos i finished so i wrote my answers on some paper and kept it to put up here:
i just wrote answers to the questions, cant remember which sub question goes with which answer so soz but yh..

1) 0.2, 3, 8000
2) 39.2, 11.76, 4.56
3) 400, 64, 26.1
4) m = 9, v = 63 (i forgot to divide it by 9 lol so v is actually 7 )
5)2.45, 36.75, string is light & inextensible, 0.4, 0.98
6) 250, 78.4, 39.2, 253, 8.91 (degrees)
7) 10i+7.5j, 053 (degrees), 40
8) 1.73

i wanna say feel free to criticise if i got stuff wrong, but dont like.. destroy me with criticism
A lot of that seems to be the same as what I got. On question 7 I think I resolved the forces. Definitely got the same for question 8, and I think the same for question 6.
18. the 1st 5 questions were really easy ans straight forward. they were worth 44 out of the 70 marks and i definately got them all! after that, it all went downhill, i found the projectile question hard and also where you had to prove P and the bearing for the helicopter! I wanted an A but dont know if i'll get it! What do you think the grade boundaries will be for an A?
19. I am kicking myself so bad right now, but i didn't put my answers to 3 sf all of the time :/ does anyone know how many marks they will knock off for this? Will it be one for every question?
20. can anyone remember what questions 1/2/3 were about? o_O

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