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# a level forces equalibrium watch

1. im really stuck on d, i just cant find out the 2 simulatanious equations,

i find it much easier when you have to find the one on the axis or when one of the ns are given to you

pic below

2. its just a matter of simultaneous equations....

look at the top equation:

try subbing that into the 2nd equation?

NB cos 20 = sin 70
3. (Original post by GHOSH-5)

its just a matter of simultaneous equations....

look at the top equation:

try subbing that into the 2nd equation?

NB cos 20 = sin 70

Yeah, though it's probably easier to work out that fraction and sub in the decimal. Subbing that exact fraction in would drive me insane.
4. wer did u get 50 and 20 from?
5. (Original post by Elimelim)
wer did u get 50 and 20 from?
90-40 = 50, which is the angle between U and the y-axis yeh? same with 20 and V
6. thank you very much, so u just have to get it to the y axis so it equals 5
7. (Original post by Elimelim)
thank you very much, so u just have to get it to the y axis so it equals 5
as said in question c).... just resolving parallel to the y-axis...
8. umm on the book it says

u = 1.82 and v = 4.08

i didnt get v when doing your formula
9. did you get U? did you type it into the calculator correctly...
10. how becuase i cant find u without v

so if v is wrong

cos 40/70 doesnt get me 4.08
11. (Original post by Elimelim)
how becuase i cant find u without v

so if v is wrong

cos 40/70 doesnt get me 4.08
hang on. have you found U?

12. i cant find u first becuase you said i have to find v then substitute to find u?
13. no. i said substitute:

into the second equation. like this:

14. Im very very confused now
15. (Original post by Elimelim)
Im very very confused now
ok i rearranged the first equation to make V the subject. i substituted that for V into the 2nd equation. we can solve it like this:

and then divide by the big bracket on the left to get U, then shove that all in a calculator. find U. and then sub back the value of U into equation 1 to get V. see?
16. but i dont get any of them answers ;s

but i dont get u as 1.82.

i get when you substiute v into the equation but after that im lost
17. hmm i get the answers in the book. is your calculator in radians?
18. so first of all you times out that bracket you posted and you should get 1.82 for u?

then u put 1.82 into the question to get v?
19. (Original post by Elimelim)
so first of all you times out that bracket you posted and you should get 1.82 for u?

then u put 1.82 into the question to get v?
the order i shoved it in the calculator:

cos40 x cos 20 =
Ans / cos 70 =
Ans + cos 50 =
5 / Ans = 1.82.. = U
Ans x cos 40 =
Ans / cos 70 = 4.08... = V
20. forgot to divide by 5 lol thanks

that is some coplicated thing compared to b4

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