Mechanics 1 P42 2014; Discussion!

[thementor]

Is there ECF in m1?

yes

 

[Oishee Asif]

Is there ECF in m1?

Quoting from the mark scheme:

Marks are of the following three types:

"M Method mark, awarded for a valid method applied to the problem. Method marks are
not lost for numerical errors, algebraic slips or errors in units. However, it is not
usually sufficient for a candidate just to indicate an intention of using some method or
just to quote a formula; the formula or idea must be applied to the specific problem in
hand, e.g. by substituting the relevant quantities into the formula. Correct application
of a formula without the formula being quoted obviously earns the M mark and in some
cases an M mark can be implied from a correct answer.

"A Accuracy mark, awarded for a correct answer or intermediate step correctly obtained.
Accuracy marks cannot be given unless the associated method mark is earned (or
implied).

"B Mark for a correct result or statement independent of method marks."

In other words, there's no ECF, so to speak. But you do get the marks for your process, so it's a... partial ECF, I suppose.
Understand?

 

[Alex10]

So I have a question. For #6, I got the correct deceleration, however is stupidly forgot to take the weight of the particle into account when finding R. So I got R=13.5 instead of 15.5N. Consequently I used this for my resolving of the Tension, which I got as 15.59N instead of 17.59N. How many marks should I expect to lose?

 

[Oishee Asif]

So I have a question. For #6, I got the correct deceleration, however is stupidly forgot to take the weight of the particle into account when finding R. So I got R=13.5 instead of 15.5N. Consequently I used this for my resolving of the Tension, which I got as 15.59N instead of 17.59N. How many marks should I expect to lose?

You'll lose 2. You'll lose two of the B marks. Get it?

 

[wizteddy13]

What's the answer of No.3? As in, TA and TB?

 

[Oishee Asif]

What's the answer of No.3? As in, TA and TB?

T2 = 11.9, T1 = 0.5

 

[wizteddy13]

T2 = 11.9, T1 = 0.5

YES! YES! YES!

Most of my friends got 3.5 and 7.5, but that comes if u don't take weight into account, and you can't just ignore weight now!

 

[wizteddy13]

Another thing? That question for distance from t=0 to t-27, what's that one?

 

[A star]

YES! YES! YES!

Most of my friends got 3.5 and 7.5, but that comes if u don't take weight into account, and you can't just ignore weight now!

i used weight but still got 3,5 and 7.5 :/

T2sin=W+T1sin

 

[Oishee Asif]

Another thing? That question for distance from t=0 to t-27, what's that one?

71.3

 

[wizteddy13]

i used weight but still got 3,5 and 7.5 :/

T2sin=W+T1sin

That shouldn't happen. TA sincos-1(2.4/3) - TBsincos-1(2.4/2.5) = 7
If u use 3.5 and 7.5 here, it equals 0.

 

[wizteddy13]

71.3

But how? The initial 8 seconds is 8 m, yes. But the equation for v is applicable from point A ONLY, not before that point. At point A, already 8 seconds has passed....so :/

 

[wizteddy13]

Guy of the year award.

Was that sarcasm or a compliment?

 

[A star]

That shouldn't happen. TA sincos-1(2.4/3) - TBsincos-1(2.4/2.5) = 7
If u use 3.5 and 7.5 here, it equals 0.

i hate myself i hate my self i wrote cos-1 and did put the value as cos.
i took cos(2.4/3) i am going to go kill myself
so this means i will lose 6 marks or 5?

 

[A star]

But how? The initial 8 seconds is 8 m, yes. But the equation for v is applicable from point A ONLY, not before that point. At point A, already 8 seconds has passed....so :/

han na after finding s(27)-s(8) or integrate it with limits 8 and 7

 

[wizteddy13]

i hate myself i hate my self i wrote cos-1 and did put the value as cos.
i took cos(2.4/3) i am going to go kill myself

Dont beat yourself up bro...I realized how to prove that a=2 for the last question...10 seconds after I handed my paper in.

 

[Oishee Asif]

Was that sarcasm or a compliment?

 

[A star]

Dont beat yourself up bro...I realized how to prove that a=2 for the last question...10 seconds after I handed my paper in.

you lst only two freakin marks i lost 6 and then 2 in Q6 and prolly 2-3 in Q7

 

[A star]

Compliment. <3
Though I'm English, and sarcasm is in my blood, I meant what I said.

jolly good

 

[wizteddy13]

han na after finding s(27)-s(8) or integrate it with limits 8 and 7

Yeah, I understand. BUT, if we use s(27), then we are finding the s covered 27 seconds AFTER the particle reached A. If we do that, aren't we overshooting the initial time frame of 0-27s? Plus, u said to subtract s(8), but those 8 seconds are BEFORE that equation for v (and hence the s equation) became viable.