Why won't any1 answer my mech 4 question! HELP

[waleedsmz]

Exam: http://www.xtremepapers.me/CIE/Internat ... _qp_41.pdf
Question: 3

Here is a little drawing I made to illustrate my question: http://imageshack.us/photo/my-images/7/mathgl.png/

Okay... I managed to get angle AP1X, we'll call it angle 1 like in the drawing, by using Lami's rule. However, the mark scheme had a very simple answer which is: cos1= 5.5/7.3 ... and it has the same value as my answer through Lami's rule..

Supposing AP1P2 equals 90', then angle 1 equals angle 3! So how in the hell is cos1=5.5/7.3

My thoughts are that it should be either sin1=sin3=5.5/7.3 or cos2=5.5/7.3

Link to mark scheme: http://www.xtremepapers.me/CIE/Internat ... _ms_41.pdf

Thanks

 

[waleedsmz]

Re: Help mechanics paper 4

No answer yet

 

[waleedsmz]

.........

 

[nisurju]

i am not sure if i can make you clear but let me give it a try.
5.5cosX+WsinX=7.3.....i)
5.5sinX=WcosX......ii)
solve these equations u will get the value of X and then W.

also,i had the same problem with this question because of ms as it was given in a complicated way!
so try to do it urself.that cosX=5.5/7.3 in a single step had made me crazy!
good luck!

 

[jafar]

hope this helps..
good luck for ur xam nd wish me luck..

 

[omerkc1]

hey,this question is easy.........vertcal forces are "w-7.3sinx=0" horizontal forces are" 7.3cosx=5.5" solving the horizontal forces you get " cosx=5.5/7.3"..................pm me if youre still confused

 

[Mueez]

but hw
tension in p1X iz 5.5 N...nd in p2X iz W N

 

[waleedsmz]

The main question here is that if we took off the right angled triangle P1XP2, We'd have angle 3 and angle 2 ... Angle 3 is supposed to be equal to angle 1 ( which is the required angle ) .. and the answer is cosX = 5.5/7.3 while cos3 = W/7.3 !!!!!!!!!!!!!!!!!

 

[Zenzenzen]

For gods sake I really do not understand this questions AGH SOMEONE EXPLAIN IT CLEARLY

 

[arlery]

Yeah same here !!

 

[maxedout]

Well this a a really simple problem! first resolve B into 2 components ie
7.3cos1.........................................................................................1=angle AP1X
7.3sin1

as the system is in equilibrium
5.5=7.3cos1

and therefore cos1=5.5/7.3

still don't get it? Ask again!!

 

[arlery]

An alternative method:

 

[waleedsmz]

Thanks everyone
And how will you get angle AP1X arlery?
That is basically my question.. I don't want to know the how we get the answer. I was to know how cos1= 5.5/7.3 while if we took off the right angled triangle P1XP2 the answer should be sin3=5.5/7.3 .... as angle 3 equals angle 1...

 

[omerkc1]

..
this should help you........................please excuse my drawing......

 

[omerkc1]

 

[omerkc1]

http://imageshack.us/photo/my-images/808/15003524.png/