HSC 2004 Truss (1 Viewer)

[Husayn]

I think that is right, I may have missed something though.

Can someone work out the Member A, I think I know how but am not 100%.

 

[SDuke]

My answer for support 1 is different to the one on the website, i got 2790N. The on the site working out is confusing.

Member A for me is 261.0N in compression?

So i'm not sure if i'm right. but if other ppl also find the website solution is wrong, i dont mind posting my working out.

 

[fakingtheday]

Support 1:

Sum the moments about Support 2 = 0
clockwise = anti
(190 x 3) + (S1 x 4) = (450 x 7) + (4000 x 2)
Support 1 = 2645N (my bad)

Member A: Method of sections

(450 x 2) = (MA x 1.73)
MA = 520.23N (compression)

 

[Husayn]

Ahhh yes the member are 2 metres, Doh!

And yes that's how I did the member A (although I used the wrong distance for members).

 

[SDuke]

Isnt the distance from S2 to the 490N force 8.5m and the distance from S2 to the 190N force 3.5m?, otherwise my working out is exactly the same as urs.

 

[Husayn]

The distance is 7m for S2 to the Force.

 

[SDuke]

which force?

 

[Husayn]

The 490 (or 450?) on the left.

 

[fakingtheday]

Ah fun days, i constantly make maths errors. I just get lucky when the time comes. It'll be funny if you guys see me stuffing up and i jsg my state ranking.

 

[SDuke]

oh i see, that makes sense. 2/2 = 1, i got it as 0.5.

In the HSC if you do these "silly" mistake could you still get marks? eg using the coreect formula and solving it correctly, but using the wrong figures.

 

[Husayn]

Yes they will give you marks for method - if you show working out they may even give you a follow on mark - not 100% sure about this though.

 

[fakingtheday]

If you do everything right except use wrong values you'll get 3 out of 4. My teacher marks papers.

 

[Husayn]

Man that is a relief....

 

[SDuke]

yeah i know wat a relief, in my trials i got basicly all the mechanic questions wrong coz i did all these dumb errors but i teacher gave me marks for working out, i just thought he was being nice...

 

[fakingtheday]

I made some silly mistakes in the trial in basically all the mechancis and got 93

 

[Husayn]

I did great with the maths in the trial - but I totally STUFFED up the telecommunications section (which was from a past paper that I SHOULD HAVE LOOKED AT) and got 70%.

 

[fakingtheday]

yeah we had an independant paper, telecommunications was 15/15 i was so proud

 

[Husayn]

Our's was out of the 2003 HSC - directly, the entire section. I think I got something like 51% for it.