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# How did you do in M2?! watch

1. (Original post by sequence123)
What sort of raw mark do you usually need for an A?
60 is usual
2. What I was saying is that for a lamina, since it has area, 'm' must equal the mass per unit area, where as for a wire it has no area, only length, so 'm' is instead mass per unit length.

This does not affect the position of the centre of mass directly because for a uniform lamina the centre of mass will always be at the same point regardless of the laminas weight, same with a wire (midpoint of each length).

sectors and arcs are the same. if you have an arched wire, you have the position of centre of mass for a uniform wire arc, (rsinθ/θ) and the centre of mass for a uniform sector lamina (2rsinθ/3θ). Those positions will not change, regardless of the masses.
3. hello all - i think it was an easy paper.
i am confident i got all right except for one question
for this one question, i just would like some people's opinion:

the coefficient of restitution question:
the mass of A=3m, B=2m, C=5m.
however for part b) where you have to show there's no collisions, i accidently used B=3m (yes very stupid mistake). and that was worth 7marks unfortunately. just wondering - how many marks would i get then out of 7? i still showed no collisions . just wrote the wrong value for the mass of B. very unfortunately mistake that i seem prone to. probably thrown my 100 out of the window and messed my chances of 600 this year
4. usually around 60/75 for an A
5. (Original post by ArVi)
for the first question, part (b) - the new max speed the car can travel up the slope - did anyone get 14∟7∟12 (thats supposed to be 14 and 7/12)?
yup..i got 14.6m/s
6. Didn't preview that one did I... the smiley face intrusions were actually meant to be

rsinTHETA/THETA and 2rsinTHETA/3THETA respectively...
7. Most probably got a B or a C
8. (Original post by Zuber)
very unfortunately mistake that i seem prone to. probably thrown my 100 out of the window and messed my chances of 600 this year

You must be devestated
9. btw did anyone find question 6c rather odd for a 2marker? i.e. the rod was replace by a longer lighter rod that extended to the mid-point of the shape. then show that the force exerted at the point A was horizontal...
i managed to do it, but with about 1/2 a page of working out!! (calculated new T=60g, and the angle was 60 between T and vertical)
10. im feelin an E comin ma way
11. (Original post by chats)
You must be devestated
i feel ignored
12. (Original post by Zuber)
btw did anyone find question 6c rather odd for a 2marker? i.e. the rod was replace by a longer lighter rod that extended to the mid-point of the shape. then show that the force exerted at the point A was horizontal...
i managed to do it, but with about 1/2 a page of working out!! (calculated new T=60g, and the angle was 60 between T and vertical)
nope was easy.... jus took moments about Midpoint of AB. and found there were no moments either way so vertical component had to be 0.
13. (Original post by hajira)
i feel ignored
you're just great
14. (Original post by chats)
You must be devestated
lol. not really. i know that personally i deserved those marks (just accidently used mass 3 instead of 2). i wish the markers could just ignore such silly mistakes!! making mistakes like that really hasnt got anything to do with maths! and i checked, when i did use the mass of B as 3m, all my algebra was perfect
15. (Original post by Zuber)
lol. not really. i know that personally i deserved those marks (just accidently used mass 3 instead of 2). i wish the markers could just ignore such silly mistakes!! making mistakes like that really hasnt got anything to do with maths! and i checked, when i did use the mass of B as 3m, all my algebra was perfect
LoL id get 100 on every paper :P everyone would
16. (Original post by Zuber)
lol. not really. i know that personally i deserved those marks (just accidently used mass 3 instead of 2). i wish the markers could just ignore such silly mistakes!! making mistakes like that really hasnt got anything to do with maths! and i checked, when i did use the mass of B as 3m, all my algebra was perfect
Well if its as hard as everyones saying then the raw mark for 100UMS could be 69/75

You might still have your 100% record
17. (Original post by chats)
you're just great
haha thanx

i was refering to my mistake that got burried in the posts lol..
how many marks was the CoM question?
18. (Original post by Syncman)
nope was easy.... jus took moments about Midpoint of AB. and found there were no moments either way so vertical component had to be 0.
ahhhhh i see (duh). my way still worked though . and i have confirmed it at home. its a different method (much longer). hopefully i should get the marks!
19. (Original post by Syncman)
LoL id get 100 on every paper :P everyone would
not really. i mean most marks on maths papers arent lost by non-mathematical mistakes (like using the wrong mass) but by a slip up in algebra, or changing a plus to minus... or so i think
20. btw, no-one has told me what they think i could get out of 7 for 5b)...anyone have any idea?

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