Question

When we stand on loose sand, our feet go deep in the sand. But when we lie down on the sand our body does not go that deep into the sand. Why?

Answer 1

Hint: Here we can apply the phenomenon the exerted pressure depends on the surface area. If the surface area is more the exerted pressure is less and if the surface area is less the exerted pressure is more.

Complete step by step solution:
We know that pressure is force exerted per unit area.
The unit of pressure is Pascal.
And mathematically, pressure is defined as$P = \dfrac{F}{A}$, where $P = $pressure, $F = $force and $A = $area.
From the above expression we can see that pressure is not directly proportional to area.
In the question it is given that,
When we are standing on loose sand our feet go deep into the sand. But when we lie on the sand our body does not sink into the sand that much.
And we need to find the reason for the above incident.
When standing on sand we apply more pressure as the area we are standing on is small. When we lie on sand our whole body occupies a much greater area than our feet. So in this case the pressure applied is less.

All these happen due to the area of contact. Here the energy that is applied on the sand is equal to our body weight.

In short we can say that the standing area of contact is lower so that the pressure exerted is greater and the contact area lying down is greater so that the pressure exerted is less.

Note: Here we have to only remember that pressure is not directly proportional to area or $P\alpha \dfrac{1}{A}$.
There are various impacts of forces of the same size on different regions.