Why can camels walk on top of sand but humans can not?

1 Answer
Feb 3, 2016

Answer:

Relative to their respective masses, camels have proportionally more foot area than humans.

Explanation:

Warning: None of the values I'm using are likely to be accurate; they are simply for demonstration. (I don't have a camel conveniently handy to weigh or measure its foot size).

Suppose sand can support #2# pounds of pressure per square inch (#(2 " lb.")/("sq.in.")#)

Suppose a man weighing #200 " lb."# has feet, each of which covers a surface area of #30 " sq.in."#

with both feet on the ground, the man's #200 " lb."# of weight will be distributed over an area of
#color(white)("XXX")2xx30 " sq.in." = 60 " sq.in."#

for an average pressure of
#color(white)("XXX")(200 " lb.")/(60 " sq.in.") ~~ (3.3 " lb.")/("sq.in.")#

Since this is greater than the amount of pressure sand can support,
the man will sink.

A camel weighing #600 " lb."# has #4# feet, each of which might cover an area of #100 " sq.in"#.

With all four feet on the ground, the camel's #600 " lb."# of weight will be distributed over an area of
#color(white)("XXX")4xx100 " sq.in." = 400 " sq.in."#

for an average pressure of
#color(white)("XXX")(600 " lb.")/(400 " sq.in.")=(1.5 " lb.")/("sq.in.")#

Since this is less than the amount of pressure sand can support,
the camel will not sink.