# M1: Post your doubts here!

Discussion in 'Edexcel' started by Mstudent, Jun 3, 2017.

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1. ### Mstudent

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I wanted to start this thread for us to discuss about any doubts in the upcomming m1 exam. best of luck guys!

3. ### husnain99

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Any tips on vectors ? Plus relative velocity stuff ?

4. ### Mstudent

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Vectors are usually a difficult topic! I kinda relate them with physics, makes them a bit easier!

5. ### Mstudent

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guys could you help me out here! Plz don't judge me cuz I was really good at mechanics BEFORE the exams started, now i FORGOT EVERYTHING , at the end of the exams! ANYONE PLEASE URGENTLY!!!

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6. ### Mstudent

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This one also guys. Only B

7. ### husnain99

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Can someone please explain the concept of limiting equilibrium ?

8. ### Mstudent

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Limiting equilibrium is when the frictional force on a body is MAXIMUM. Let me give you an example:

Imagine you had your mobile phone on your past paper booklet and the booklet is horizontal. Now tilt the booklet a bit, does it move? NO it doesn't because friction is NOT MAXIMUM and the force of gravity on the mobile phone along the booklet is EQUAL to the frictional force and the mobile is in EQUILIBRIUM (NO RESULTANT FORCE!). Tilt the booklet a bit more, stop JUST before the mobile starts to slide on the booklet, at this point the Frictional force is AT ITS MAXIMUM and is EQUAL to the force of gravity on the mobile along the booklet and its STILL IN EQUILIBRIUM, but it is at the point of sliding along the booklet, the friction is JUST ENOUGH to keep the mobile at equilibrium from sliding down, thus LIMITING EQUILIBRIUM (This is the maximum limit for the friction to prevent the mobile moving!)

Hope this helps.

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9. ### husnain99

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10. ### Mstudent

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you're welcome anytime

BTW could you plz, help me with my questions above?

11. ### husnain99

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Btw after that , ( I mean when friction force is at its maximum and the mobile is on the point of moving ) will friction force change while the mobile is sliding down ? ( given that the booklet is rough )

12. ### husnain99

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I covered vectors like a month back and have to revise again
Can help with pully question ..

13. ### Mstudent

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When the frictional force becomes maximum, it stays CONSTANT even if the weight of the mobile along the book (if angle along horizontal) is increased. So to find the maximum in this case, use F=uR

hope that helps

14. ### Mstudent

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Yo, will this be accepted if I write

T - 3g = 3ma
2mg - T = 2ma

15. ### husnain99

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I don't think so ..
take overall mass on other side too ..

Cause if you take only 2m on the other side then how A can move upward ?

16. ### husnain99

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In this qs did you get your Part A correct ?
Can u tell me why they're taking F as positive and not negative while making equation of motions ???

Btw part B is repeated concept : use cosine rule that's the easiest method ...

17. ### Mstudent

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Yeah I did part A and I got it correct. I have an easier method for b). You use 2T Cos(theta/2). My teacher told me about it.But how do you find the angle in this case?

18. ### Mr.Physics

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hey from which paper is this question?
the P and Q particles one

19. ### Mstudent

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june 2015

20. ### husnain99

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How the M1 today ?
What was the answer for T in kinematics question ?

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