There's a thing called Google.Is there a difference between truss girder and box girder bridges ? Is a box girder just more specific ? If so what would each look like. What makes a truss girder bridge different from the rest ?
On the Excel Senior High School Engineering Studies (author by Peter M & Roger M) text book page 28, where I'm introduced to the Engineering Mechanics and Hydraulics, there's an example where the area is divided by 4.
I'll rewrite the work:
Tensile stress
Determine the Ultimate Tensile Stress (UTS) of a 15mm diameter rod if the maximum load it can withstand is 70 kN.
Load = 70k x 10^3 N
Diameter = 15 mm
Area = pi15^2 divide by 4
= 176.7 mm^2
...and then it continues with
UTS = L/A
But I want to know where the "divide by 4" comes from?? Is this textbook even reliable?
I don't think I'll ever work out what exactly it is you do lol
Here's what I get.Hai again. I'm irritated at a question and I'm not entirely sure how the conversion thing goes. I've got the numbers right but I don't got the numbers in the right places... See below:
It's from a book called Engineering Studies The Definitive Guide.
Q. Find the resistance of a copper wire used in an appliance that is 300mm long, and has a diameter of 2mm, if the resistivity of copper (at 20oC) is 1.7x10-10 Ohm metre.
The formula given is R = p x l/a
where
R is the Resistance (Ohm)
p is the resistivity (Ohm m)
l is the length (m)
a is the cross sectional area (m2)
Here's my work out:
R = (1.7x10-8) x (0.3)/ pi(3.141...) x 0.001
= 0.00000162338 Ohm
And, the answer given was 1.62 Ohm m
I thought I got the conversion wrong but I'm really not sure now.