Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A steel beam rests on supports apart. Its cross-section is wide and deep. A load of sits at its middle. How far does the middle sag? How far would it sag laid on its side (6 cm deep and 12 cm wide)? (.)
Safety factor breaking stress largest working stress. A beam on two supports with a load at its middle sags . Rock at the base of a mountain of height carries a stress , which limits to .
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. On edge. .
Step 2. Laid flat. becomes , four times smaller, so .
Answer: on edge; laid flat.
Check. The ratio is .
Watch out. The depth is the side in the direction of the load.
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