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OCR MEI AS Mathematics M1 10/06/2013

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Reply 120
Original post by johndoe4
Wait... i got like 1.44s on the last question

views on that?


The quadratic retrieved two values 1.34 and 7.67 me thinks
Abi can die in a hole.
Reply 122
Original post by johndoe4
i got 7/0.4= 17.5


wasnt it like (0, something, 17.5)
Reply 123
Original post by Axion
The quadratic retrieved two values 1.34 and 7.67 me thinks
what if you usedf v=u+at is that wrong? to get 3.5s
Reply 124
Original post by Axion
The quadratic retrieved two values 1.34 and 7.67 me thinks

1.34 or 1.44 cant remember....but it could only be one time so you use the -b+the root

7.67 seems a little long tho

i think
Reply 125
Original post by Axion
wasnt it like (0, something, 17.5)
i got (0,0,17.5) :s-smilie:
Reply 126
Original post by JG1027
what if you usedf v=u+at is that wrong? to get 3.5s


Except you don't know v? I think that's where u may have slipped. We do know s though

(btw i got it wrong so maybe lost 2-3 marks :P)
Reply 127
Last Question:
Only force acting down was gravity, where a = -gsin15
The inital velocity is 8 and the inital displacement is 13.
Hence v = -gtsin15 + 8
And s = -0.5gt²sin15 + 8t + 13
Set s = 0 to get t = -1.34025 or t = 7.64833
As t must be positive, the time is 7.65 seconds.
(edited 10 years ago)
Reply 128
Original post by johndoe4
1.34 or 1.44 cant remember....but it could only be one time so you use the -b+the root

7.67 seems a little long tho

i think


was the sledge being pushed up or down the slope?
Reply 129
Original post by Axion
Except you don't know v? I think that's where u may have slipped. We do know s though

(btw i got it wrong so maybe lost 2-3 marks :P)
thing is isnt v=0 as it goes down the slope so it must come to rest?
Reply 130
Original post by Axion
wasnt it like (0, something, 17.5)


How did you answer that vector equation?
I think I did r-p-q-weight=ma
Weight being vector (0,-4,0) :/
(edited 10 years ago)
Reply 131
Original post by Axion
wasnt it like (0, something, 17.5)

What direction did you put.

i added all the forces and got (0,0,7) so magnitude = 7newtons=ma
Original post by JG1027
i did that but i used v=u+at to find the time would that be wrong? because v=0 u=8 a=2.5 and t=? so rearrange and i got -3.2s so 3.2 s :frown:


well firstly the accelaration and velocity would be in different directions so at least one must be negative...
and also that equation wouldnt work out how long it took to the bottom it would work outhow long it would take to reach v=0 at the top of the slope not at the bottom of the slope...
Reply 133
Original post by ayloedxa
Last Question:
Only force acting down was gravity, where a = gsin15
The inital velocity is 8 and the inital displacement is 13.
Hence v = gtsin15 + 8
And s = 0.5gt²sin15 + 8t + 13
Set s = 0 to get t = -1.34025 or t = 7.64833
As t must be positive, the time is 7.65 seconds.

NONONO there was definitely a negative in the quadratic somewhere
Reply 134
Original post by Jojo_555
How did you answer that vector equation?
I think I did r-p-q-weight=ma
Weight being vector (0,4,0) :/


yeah weight was defo that vector.

aff em all together and divide by 0.4
Original post by Axion
yeah weight was defo that vector.

aff em all together and divide by 0.4



Why is weight not (0,0,4)?


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Reply 136
first we addd all the forces to get the resultant. as vectors have direction and mag you just add. then =ma
Original post by johndoe4
first we addd all the forces to get the resultant. as vectors have direction and mag you just add. then =ma


Yeah but mg in this case is 0.4x(0,0,10), no?


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Reply 138
Original post by Axion
yeah weight was defo that vector.

aff em all together and divide by 0.4


I don't get why they are added together....I thought cuz r had the biggest magnitude, you take them all away from r. I think I've screwed that question up aswell T.T
Reply 139
Original post by stefanocattaneo
Why is weight not (0,0,4)?


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True. Am not sure tbh. I normally always take it in the j direction but could be wrong

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