Flat shoes vs high-heel shoes
Fig. 6-5: Stresses exerted from flat and high-heel shoes
(Courtesy of Miss C Patel) [6.2]
A woman wearing high-heel shoes or flat shoes will exert the same force on a floor but with significantly different stress levels. Fig. 6-5 shows a woman weighing 50 kg wearing flat shoes (a) and high-heel shoes (b). The stresses exerted by the shoes can be estimated as follows:
Flat shoes: The contact area of one of the flat shoes (Fig. 6-5a) is 
. Assuming the body weight is uniformly distributed over the contact area, the average stress is:
High-heel shoes : Assuming that half of the body weight is carried by the high-heels (Fig. 6-5b); each high-heel carries a quarter of the body weight. The area of the high-heel is 
. Thus the average stress under each high-heel is:
This shows that the stress under the heels of the high-heel shoes is about 60 times that under the flat shoes.
A typical adult elephant has a weight of about 5000 kg and the area of each foot is about 
. Thus the average stress exerted by an elephant's foot is:
Elephants have large feet to distribute their body weight. The stress exerted on the ground by the foot of an elephant is much less than that under the high heel shoes.