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# M1 TOMORROW 11.30 lol, really need clarification watch

1. If resolving forces on horizontal. It says it is at point of slipping how do you know if uR is acting up or down??

Rep for month for best answer

Honestly though,all suggestions needed..
2. is the plane flat or at an angle? if you give me more information i'll be able to help. If it's a slope though friction will be acting up if it's about to slip down
3. Friction always acts opposite to the direction of motion.
4. (Original post by MedAmy)
If resolving forces on horizontal. It says it is at point of slipping how do you know if uR is acting up or down??

Rep for month for best answer

Honestly though,all suggestions needed..
Is it on a slope?

If the it's going to move down the slope then uR will act in the opposite direction to motion.
5. (Original post by ebyrne288)
is the plane flat or at an angle? if you give me more information i'll be able to help. If it's a slope though friction will be acting up if it's about to slip down
ok if you have the paper handy its Q5 jan 2009. But if not no worries.

Jus generally if the plane is at an angle. Ok, then it says force P acting at an angle. Then you have it (a) point of sliding down
(b) point of moving up plane

what im asking it how do you know when up is goin up or down.
What i think is;

point of sliding, it acts same direction with force P.

and vice versa for sliding up???
6. (Original post by MedAmy)
ok if you have the paper handy its Q5 jan 2009. But if not no worries.

Jus generally if the plane is at an angle. Ok, then it says force P acting at an angle. Then you have it (a) point of sliding down
(b) point of moving up plane

what im asking it how do you know when up is goin up or down.
What i think is;

point of sliding, it acts same direction with force P.

and vice versa for sliding up???
I'm not entirely sure what you're asking, but, for that question: when it's on the point of sliding down the plane, friction will be acting up the plane; when it's on the point of sliding up the plane, friction will be acting down the plane.
7. what board is it?
when it is at the point of sliding down the plane then uR will act up the plane
when it is at the point of sliding up the plane then uR will act down the plane
it is always in the opposing direction of motion
8. Go to sleep .. no point worrying now ... youll lose more marks if you dont go to sleep then asking for help ....
9. Gravity acts down. So on a slope, it will have component trying to pull it down the slope.

Your force P must presumably be acting such that it has a component up the slope. Otherwise there is nothing to push it up and it won't be on the point of sliding up.

If something is moving, friction wants it to stop. If something it stationary, friction wants it to stay that way. So if you're trying to push it up the slope with your force P, friction will be acting down (parallel to) the slope, trying its best to stop the object sliding. Friction has a maximum value here and so on the point of slipping up, it is at its maximum value pointing down, and the forces are in equilibrium. Then if you increase P a bit, friction can't increase any more and so there will be a resultant to accelerate the force up the slope.

As you decrease P from the situation where the object is on the point of slipping up, friction will decrease in order to maintain equilibrium (wanting to keep the object still), until it is zero and then is pointing up the slope. On the point of slipping down, friction is at its maximum value pointing up the slope, trying to stop the object from slipping.
10. THANKS EVERYONE.. I FULLY Understand..

just one more thing, if you would.

When finding resultant of vectors. do you add them?
11. what you do is split the vectors into the horizontal and vertical components. If they are in the same direction then you add them, if they are in opposite directions then you take them away
this will leave you with a resultant horizontal and resultant vertical component. to find the resultant of these, you find the square root of the horizontal component squared plus the vertical component squared i.e. Phythygoras' Theorm

hope that made sense. if it didn't i'll try to make it simpler
12. 11.30 exam?

13. (Original post by ebyrne288)
what you do is split the vectors into the horizontal and vertical components. If they are in the same direction then you add them, if they are in opposite directions then you take them away
this will leave you with a resultant horizontal and resultant vertical component. to find the resultant of these, you find the square root of the horizontal component squared plus the vertical component squared i.e. Phythygoras' Theorm

hope that made sense. if it didn't i'll try to make it simpler
hiya.. aw thanks for helping me Ebyrne, at this time of night..
you know yourself exam panicing.. lol

Oh yep, that's great never knew you did that, i did it slightly different. But taking your method into account, how do you which is in which direction does it tell you, or do you look at the - / +??
14. if force is acting up the plane= friction will act down plane
Vice versa
15. (Original post by *MJ*)
11.30 exam?

nope it was 11.30 when i posted the thread.
16. you take one direction to be positive, for example with the horizontal component take right as positive and left as negative. if your answer is positive then you know it's to the right, and if it's negative it's to the left

it's no bother
i have a maths exam tomorrow too C3 but I can never sleep before exams. plus it's not til the afternoon
anything else? i don't mind
17. (Original post by ebyrne288)
you take one direction to be positive, for example with the horizontal component take right as positive and left as negative. if your answer is positive then you know it's to the right, and if it's negative it's to the left

it's no bother
i have a maths exam tomorrow too C3 but I can never sleep before exams. plus it's not til the afternoon
anything else? i don't mind
ah thanks **
well, im still a bit confused about taking one to be + or -..you are never given info to do that, or are you?

like if a force is acted upon by F1 and F2. Do you add these?

R is parrallel to i does that mean you let j=0?

oh and if you want to show that two vectors meet, and you must calculate that vector, what do you do??

Ah is C3 Edexcel on tomorrow??
18. naw you just have to assume one yourself. I just take up and right to be positive, and down and left to be negative

one you have resolved F1 and F2 into the horizontal and vertical component, then you add the two horizontal components together, and the two vertical components together. Then you find the resultant of these two by Pythygoras' Theorm

I'm CCEA so my syllabus is a bit different, but that sounds right what you said about j = 0 when R is parallel to i
can you give me an example of a question about two vectors meeting. I've not done it before but I can imagine how it would be done
19. (Original post by ebyrne288)
naw you just have to assume one yourself. I just take up and right to be positive, and down and left to be negative

one you have resolved F1 and F2 into the horizontal and vertical component, then you add the two horizontal components together, and the two vertical components together. Then you find the resultant of these two by Pythygoras' Theorm

I'm CCEA so my syllabus is a bit different, but that sounds right what you said about j = 0 when R is parallel to i
can you give me an example of a question about two vectors meeting. I've not done it before but I can imagine how it would be done
okies.. what do you mean by reloving F1 and F2 into the horizontal and vertical component, stil confused.
I understand the rest though...

Ah i just looked at mark scheme.. think i can follow it now*meeting Q*.

ah the joys of ccea, chem & bio no p/s books.. module 4 27th? looking forward to it?lol
20. F1 and F2 are forces aren't they? If they don't act on a body parellel to i or j, then the vertical component will be Fsinx and the horizontal component will equal Fcosx where x is the angle the force makes with the horizontal plane
maybe I've misunderstood what you're asking

my exams have come in blocks close together. I had one yesterday, one tomorrow and one coming on monday, then my next exam isn't until chemistry, then physics the next day and M2 the following monday, so at the minute I'm just focusing on C3 and English. my teacher is so awful though, a lot of my class were repeating module 1 today

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