Physics question! Plz answerr! VERY IMPORTANT

[gotchaeme]

One species of dinosaur had a mass of about 1500 kg, as it walked, could support its whole weight on a single leg bone of length 75cm. If the breaking stress of the bone is 1.8 x 10(the 10 is to the power of 7) Pa then the minimum diameter the leg could have been to support the animal without fracture is?

I need the answer and ALL the workings out....
It is very important and is needed ASAP
Thankss Btw its either a,b,c or d

(a)1.6cm
(b)2.8cm
(c)3.2cm
(d)4.8cm

[gotchaeme]

Thankk youu,
youve like saved my life haha i needed this question to get the mark i was aiming for =]

[gotchaeme]

Thank youu!! ^_^

Saved my lifee!

Well my grade =P

[Pigletion]

hope I got it right!

The logic is sound, just need to point out that you are assuming a uniform leg that is an incompressible solid (you have to, as you are not given any information in the question to suggest otherwise), so a force applied to a 1 cm leg has the same affect as a force applied to a 75 cm leg, as the area is constant. Therefore assuming weight is acting vertically downwards.

Don't know if you get asked about assumptions, sometimes they do in exams.

PS Bones would not actually be solid in cross-section and they would have various points of weakness etc. and also aren't perfectly cyclindrical, but you have to transform the problem into something you can apply logical reasoning too.

OK, will shut up now as I don't want to confuse the issue (too much!)

[gotchaeme]

now im confused.com
haha
ill let you know how i do =]

[Pigletion]

Good luck!