Mechanics 1 P42 2014; Discussion!

[thementor]

Hahah, true. Or, more likely, a cerebral infarction, when we can't even think straight

Yeah I'd go with a cerebral infarction. Or maybe an epidural hemorrhage.

 

[Oishee Asif]

(Was I the only one thinking about Death Note here?)

 

[Mujjix113]

Discuss privately in PM!!
Paper was alright, but q7 was long and q2 was fucked up!!..:/..
Rest was lengthy...Damn you new paper pattern!!...Damn you to eternal hell!!

What was question 2 again? the 10m one ?

 

[wizteddy13]

(Was I the only one thinking about Death Note here?)

Nope, I thought of it too. *high 5*

 

[Oishee Asif]

Nope, I thought of it too. *high 5*

*High fives you, after offering you a civilised beverage: tea*

 

[Oishee Asif]

What was question 2 again? the 10m one ?

Yeah.

 

[wizteddy13]

*High fives you, after offering you a civilised beverage: tea*

Ah, dem Brits with their tea. *accepts*
*takes tea to study table*

Physics time now, l8r

 

[qwerty123123]

can anyone remember what q2 was?

 

[Oishee Asif]

Ah, dem Brits with their tea. *accepts*
*takes tea to study table*

Physics time now, l8r

*bids you farewell*

Yeah. Maths P3 for me.

 

[Ahmedlool]

Guys if i got a 24 out of 50 in mechanics and got a 64 out of 75 in pure. What would my overall grade be??

 

[usama321]

Nope, I thought of it too. *high 5*

71.3 is the correct answer. Oishee has solved it for you by one of the two possible methods, I'll solve it with the other method to assure you.

Disance in the first 8 seconds was 8 m. We would integerate the second equation, with the constant, and equate it to 8, and get the value of C

0.3 t^5/3 + c = 8
0.3 (8)^5/3 + c = 8
c = -1.6

Now, that you have the value of C, just switch in the value of 27
0.3(27)^5/3 -1.6 = 71.3

 

[Mootaz]

Can someone post the answers of all of the questions +working ?

 

[hamaas]

i messed up q3 and use lamis thoerem will i get marks for this?

 

[17194]

71.3 is the correct answer. Oishee has solved it for you by one of the two possible methods, I'll solve it with the other method to assure you.

Disance in the first 8 seconds was 8 m. We would integerate the second equation, with the constant, and equate it to 8, and get the value of C

0.3 t^5/3 + c = 8
0.3 (8)^5/3 + c = 8
c = -1.6

Now, that you have the value of C, just switch in the value of 27
0.3(27)^5/3 -1.6 = 71.3

This would only work if the velocity of the body from the start was 1/2 T^2/3, when in fact, in the beginning the velocity was changing linearly.

i messed up q3 and use lamis thoerem will i get marks for this?

I can't imagine you will get much credit for it. Lami's theorem can only be used in the case of 3 forces. The ring had weight, a rightwards force of 10N and the tension in 2 strings acting on it, making a total of 4 forces. You had to resolve the components and equate them.

 

[Ahmedlool]

sadly no i did that aswell so far i got 25 mistakes....Guys if i got a 24 out of 50 in mechanics and got a 64 out of 75 in pure. What would my overall grade be??

 

[17194]

sadly no i did that aswell so far i got 25 mistakes....Guys if i got a 24 out of 50 in mechanics and got a 64 out of 75 in pure. What would my overall grade be??

Well according to last year's grade threshold an A was at 93 and a B was at 79, so you would have a B. But then again, it depends upon the grade threshold for this year.

 

[usama321]

This would only work if the velocity of the body from the start was 1/2 T^2/3, when in fact, in the beginning the velocity was changing linearly.

I can't imagine you will get much credit for it. Lami's theorem can only be used in the case of 3 forces. The ring had weight, a rightwards force of 10N and the tension in 2 strings acting on it, making a total of 4 forces. You had to resolve the components and equate them.

It has nothing whatsoever to do with the velocity of the body. It's about the displacement. Check other past papers and you will understand.

 

[Ahmedlool]

thnx....was hoping for an A but ohwell allhamdullilah

 

[usama321]

This would only work if the velocity of the body from the start was 1/2 T^2/3, when in fact, in the beginning the velocity was changing linearly.

I can't imagine you will get much credit for it. Lami's theorem can only be used in the case of 3 forces. The ring had weight, a rightwards force of 10N and the tension in 2 strings acting on it, making a total of 4 forces. You had to resolve the components and equate them.

You do know there is a reason for finding out the constant. It makes the equation applicable to the first 8 second as well. It is just like finding the equation of a curve when you have it in the form of dy/dx. Once you find the value of the constant c, you can put in the whole 27 seconds and you will get the right answer

 

[A star]

i messed up q3 and use lamis thoerem will i get marks for this?

depends on only one thing if you included weight. Yes then it will be full marks given you do it correctly but i triedit but gave up after the first thought