Question

Arasu went to an exhibition. There he saw a magician lying on a bed of nails. To his wonder, the magician was not hurt at all. Help Arasu to understand the phenomenon.

Answer 1

Hint: Use the relation between pressure, force and area of cross-section. The pressure experienced by the force F is inversely proportional to the cross-sectional area on which the force is applied.

Formula used:
\[P = \dfrac{F}{A}\]
Here, P is the pressure, F is the force and A is the cross-sectional area.

Complete step by step answer:
We know that the pressure is the applied force divided by the cross-sectional area on which the force is applied.
\[P = \dfrac{F}{A}\]
Suppose the mass of Arasu is 50 kg. Then the weight of Arasu is the gravitational force exerted on Arasu. In this case, the applied force is the weight of Arasu.
Suppose Arasu steps on a single nail of cross-sectional area A which will be very small. Since the pressure is inversely proportional to the cross-sectional area, the pressure exerted by Arasu on the nail will be large and of no surprise, the nail will hurt his leg.
A bed used by a magician is made such that a number of nails are placed close to each other. Thus, by increasing the number of nails on the bed, the cross-sectional area is increased. Therefore, the pressure exerted by the magician on the nails is reduced by the greater extent and he does not get hurt at all.

Note:
For a magician to not get hurt, the nails placed on the bed should be very close to each other so as he steps on the maximum number of nails.