they’d either be very stocky or all break their ankles.
Suppose there were giants on Earth. As in things that were built basically like humans, but ten times taller so that they could look over small trees. They’d all have broken bones all the time.
First, a caveat. I am not trained in either physiology nor civil engineering; the derivations below are for illustrative purposes only.
Bones act like both columns and beams. The physics of each is different, but the end result is the same.
The stress placed on a beam is determined by
|width × load × length|
|10 × 1000 × 10|
Columns buckle when the load on them exceeds a factor proportional to
So, what if we make the giant’s stockier? Increasing width but not height by a factor of w increases load by w2 and area moment of inertia by w4, so the stress on a beam changes by
|w × w2|
The above assumes we increase all width (that’s what made the load increase so quickly). If we only increased the girth of the bones, not anything else, we’d still have stocky giants and ones that look like skeletons to boot. If total body mass is M and skeleton mass is sM then the change in load from a w-increase in bone width is
|w × (1 − s + sw2)|
Of course, they might be wider than they are tall and thus incapable of moving, or they might suffer chronic broken bones. but if you see a giant that looks like anything other than a stocky skeleton, fear not: they’ll snap their bones just walking.