Engineering 2005 multichoice URGENT help (1 Viewer)

[cloud edwards]

Does anyone know how to do question 9 of the 2005 Engineering HSC exam and provide solutions.The question about Bending moments.

I know so far:
4.17 × 10^6 mm^4 (SI units)
F=My/I
I'm unsure about y since it says "maximum bending stress on the bottom edge of the beam"

Please help!
PAPER:
http://www.boardofstudies.nsw.edu.au/hsc_exams/hsc2005exams/pdf_doc/engineer_studies_05.pdf

 

[dan964]

http://www.boardofstudies.nsw.edu.au/hsc_exams/hsc2005exams/pdf_doc/eng_stud_er_05.pdf

has MC answers.

 

[D94]

Does anyone know how to do question 9 of the 2005 Engineering HSC exam and provide solutions.The question about Bending moments.

I know so far:
4.17 × 10^6 mm^4 (SI units)
F=My/I
I'm unsure about y since it says "maximum bending stress on the bottom edge of the beam"

Please help!
PAPER:
http://www.boardofstudies.nsw.edu.au/hsc_exams/hsc2005exams/pdf_doc/engineer_studies_05.pdf

No.

sigma = My/I

where sigma is bending stress, M is bending moment, y is centroidal distance, and I is second moment of area.

The moment, M, is about the centre, so M = Fd = F(2000).

y is about the centroid of the cross section = 50mm, and sigma is given as 42MPa or 42 N/mm^2.

Sub those into the equation and rearrange to find F.

The answer is D, 1751.4N