Eggshell Tripod
Eggs have such thin shells they almost appear flimsy.
Yet nature designed the egg shells as a strong vault to protect the live embryo inside.
Shell structures are usually very strong and you can test this using three broken eggshells.
Using scissors nip the eggshells bit by bit to even out the zigzags and to get a circular rim.
Carefully rub the circular rim on the cement floor to even out the remaining zigzags.
Place three such eggshells on a doubled up towel, which will act as a cushion.
Now make a guess estimate of the weight which this eggshell tripod will be able to withstand.
Keep placing books on the tripod until the eggshells crush under their load.
How close was your guess?
Nature is very economical in its use of material.
Human beings have learnt a great deal about structures from nature’s optimal designs.
Ray models
Punch out three holes 5 cms apart on an old rubber slipper (Fig 1)
Press fit 20-cm long phooljhadu sticks or pencils in these holes.
When the slipper is lying flat, the sticks stand upright (Fig 2) Suppose the slipper is a plain mirror strip, the light rays striking it at right angles will retrace their path as in ray diagram (Fig 3)
What would happen if instead of a plain mirror you had a concave mirror?
Just bend the rubber slipper inward and see.
The three sticks now converge at a point called the focus (Fig 4).
What would happen if instead of a plain mirror you had a convex mirror?
Just bend the slipper the other way and you’ll see the sticks diverging (Fig 5).
As glass cannot be flexed and rays are invisible, this model will be of some help in concretising the concept of ray diagrams through curved mirrors.
(Excerpts from Little Science by Arvind Gupta. Read the entire book on arvindguptatoys.com)
