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# M1 Statics Watch

1. I cannot understand why I am wrong with this question. I just don't see the mistake I've made.

QUESTION 5

https://3b0a7b1bc87f5381e60f8f717510...%20Edexcel.pdf

http://imgur.com/2ub4kcB

Here is my working for the value of P, am I blatantly missing something? Guidance plz
2. (Original post by xyz9856)
Here is my working for the value of P, am I blatantly missing something? Guidance plz
You're meant to be resolving horizontally and vertically. Not perpendicular and parallel. This is the case for these types of questions when you have a horizontal force acting.
3. (Original post by Zacken)
You're meant to be resolving horizontally and vertically. Not perpendicular and parallel. This is the case for these types of questions when you have a horizontal force acting.
I dont understand, why would that make a difference?
4. (Original post by xyz9856)
I dont understand, why would that make a difference?
If you resolve vertically, this will let you find the value of R (normal reaction) directly since you will be able to ignore the horizontal components.
5. (Original post by xyz9856)
I cannot understand why I am wrong with this question. I just don't see the mistake I've made.

Here is my working for the value of P, am I blatantly missing something? Guidance plz
You can resolve in any direction, but some are easier to work with than others.
I've not checked, but assume as Zacken said, it's easier to resolve horizontally and vertically.

That said, perpendicular and parallel should work. From looking at your working, the mass is on the point of slipping down, so friction will act up the plane, and as such your second line should have +R/2, not -R/2. Not checked the rest.
6. (Original post by ghostwalker)
You can resolve in any direction, but some are easier to work with than others.
I've not checked, but assume as Zacken said, it's easier to resolve horizontally and vertically.

That said, perpendicular and parallel should work. From looking at your working, the mass is on the point of slipping down, so friction will act up the plane, and as such your second line should have +R/2, not -R/2. Not checked the rest.
Ah, that makes sense I should have paid more attention to the question, thank you

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