Question

in the first lecture mass is proportional to size cubic
my question is : why cubic??

Answer 1

IMO, if you look at it from a one dimensional and two dimensional standpoint, you start with a point, and let it grow in one dimension becoming a line. The line has no mass, as it has no volume. Then let the line grow in a second dimension becoming a plane. But it still has no mass as it has no volume.

Answer 2

I should probably also add that he is approximating the size of a body as a cube, discarding all the details of arms, legs, etc.

Answer 3

in cube
V = L^3
M is proportional to V
so M is proportional to L^3
but I don't understand whta he means by "size"

Answer 4

It just means the same thing, I guess. L^3=size cubic