Question

Why can you push a drawing pin into a surface using your thumb when you can’t push your thumb into the same surface?

Answer 1

Hint: Pressure applied on an object is inversely proportional to the area of that object. A drawing pin has two ends, one with a sharp tip and the other with a wide portion. Because of the pin's tiny surface area, the sharp tip exerts a lot of pressure.

Complete answer:
relation between pressure on an object and the area of that object is
$\text{Pressure} = \dfrac{\text{Force}}{\text{Area}}$
From here we can say if an object has less area it can exert more pressure on the surface and gets pierced easily on the surface.Drawing pins have thin and pointed ends because the smaller surface area of the tip generates more pressure, making it much easier to push the drawing pin into a surface.

Whereas our thumb in comparison to the drawing pin has a larger surface area, so it does not exert as much pressure on the surface as the drawing pin. More force is required in order to push our thumb into the surface but that can break our thumb.

Hence, we can push a drawing pin into a surface using our thumb but can't push our thumb into the same surface.

Note: A drawing pin is made in such a way that one end is kept wide while the other is very sharp. This is because when piercing a drawing pin, some external force must be applied to the upside of the pin in order for it to be pierced. The head must be wide in order to apply more force.