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# Official OCR A G481 mechanics 20th May 2013 Watch

1. (Original post by OllieGCSEs)
Seatbelts/airbags:

The time taken for the driver to stop is increased using both airbags and seatbelts. An increased change in time results in a decrease in acceleration (as a=(v-u)/t, but you don't really need to say this), and a decrease in acceleration results in a decrease in force due to F=ma. Also they both prevent collisons with the windscreen/steering wheel

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tnx, do you have a worked questions for this topic ??

I haven't got class tomorrow morning, I am trying to completely understand this topic.
2. (Original post by Majjie)
Hope everyone does well tomorrow!
Same to you!
3. good luck everyone stay calm and do well
4. Good luck all. Still trying to sleep ;P

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5. sleeping is hard, although its good thing that its at 2!
6. can anyone explain how to do 1)a)iii) on jan 2009? I understand that when the area of both graphs will be equal, A will overtake B, but I don't understand how they got (0.5 x 3.5 x tsquared) - I'm assuming it's from the area under the triangle but I don't get how the 3.5 got there
7. (Original post by Kreayshawn)
can anyone explain how to do 1)a)iii) on jan 2009? I understand that when the area of both graphs will be equal, A will overtake B, but I don't understand how they got (0.5 x 3.5 x tsquared) - I'm assuming it's from the area under the triangle but I don't get how the 3.5 got there
I struggled with it last night too, on the marking scheme they substituted but I don't understand why..
8. so during a crash the crumble zone allow for an increased breaking distance of the driver and thus reduces the braking force on the driver ?

is this really sufficient
9. good luck everyone i'm hoping for an easy paper, first time doing this paper and I am really nervous
10. Goodluck everyone! We can do it
11. Good luck everyone, hope it goes well for you all.
12. Good luck guys!
13. (Original post by ss2012)
I struggled with it last night too, on the marking scheme they substituted but I don't understand why..
Hi guys'll
Basically look in your books for proving the s = it + 1/2at^2 equation from
The graph. Your are than mirroring this in the question of course leaving the time as the unknown.

I can't remember the question exactly but if you don't get it still pm with the question
Hope it helps

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14. (Original post by Munrot07)
good luck everyone i'm hoping for an easy paper, first time doing this paper and I am really nervous
same ;(

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15. (Original post by ConfusedChild123)
PLEASE HELP URGENT HELP quick question how many times can you resit physics mechanics unit 1 ocr as level exam I'm resitting this exam in may however was wondering if it is possible to resit the exam once again during my A2 Year. So resitting the exam twice and was wondering if i could do that for chemistry to?

i dont think there is a limit, a guy in my year is on his 5th try!!!
16. Does anyone believe that the experiment to determine g will come up?
17. (Original post by Kreayshawn)
can anyone explain how to do 1)a)iii) on jan 2009? I understand that when the area of both graphs will be equal, A will overtake B, but I don't understand how they got (0.5 x 3.5 x tsquared) - I'm assuming it's from the area under the triangle but I don't get how the 3.5 got there
use s=ut+0.5at^2
for A
s=s
u=10 -> therefore s=10t +(0.5 x 3.5 x t^2)
v=24
a=(24-10)/4=3.5
t=t
for B
s=s
u=14 -> therefore s=14t
v=14
a=0
t=t

let both s equal each other then solve to find t ....

hope this helps xxx
18. (Original post by mickymouse1995)
use s=ut+0.5at^2
for A
s=s
u=10 -> therefore s=10t +(0.5 x 3.5 x t^2)
v=24
a=(24-10)/4=3.5
t=t
for B
s=s
u=14 -> therefore s=14t
v=14
a=0
t=t

let both s equal each other then solve to find t ....

hope this helps xxx
Why are you taking the area of A's triangle and not the whole trapezium. What if A overtook B when A was at constant velocity
19. the stress is kicking it  what time is everyone doing the exam at?
20. (Original post by ss2012)
the stress is kicking it  what time is everyone doing the exam at?
Tell me about it mines at 1:30.
I just got a call for a phone interview whilst I was revising this morning, I might as well have screamed down the phone and hung up :l
I have a feeling this one is going to be harder then the January one, although I am much better prepared now.

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