Question

The yield point of a typical solid is about 1%. Suppose you are lying horizontally and two persons are pulling your hands and two persons are pulling your legs along your own length. How much will be the increase in your length if the strain is 1%? Do you think your yield point is 1% or, much less than that?

Answer 1

If the height is H and the increase in height/length is h due to pulling then the strain =h/H. If it is 1% then h/H = 1/100 

→h = H/100 

If the height H = 180 cm (say) then the increase in length h = 1.80 cm.  

Since our body has joints which are weaker than the bones so this increase in length will be located to the weakest joint. Any joint having 1.80 cm separation will be much damaging. So the yield point (or the bearable pain) due to pulling will be much less than 1%.