Question

Consider what happens when you push both a pin and the blunt end of a pen against your skin with the same force. Decide what determines whether your skin is cut—the net force applied to it or the pressure.

Short answer

The pressure exerted on the skin determines whether the skin is cut or not.

Step-by-step solution

Understanding the concept of pressure

The expression to find the pressure exerted on a given area is:

In other words, the pressure exerted is the force applied in a unit area.

Analysis of the situation and conclusion

For both the pin and the blunt end of the pen, the applied force is the same. In the case of a pin, the surface area of its tip is very small compared to the blunt end of the pen. Therefore, the pressure exerted by the pin on the skin is larger than the pen.

So, the pressure determines whether the skin is cut or not.