Introduction:
When a pencil is sharpened at one end and pressed between the index fingers of both hands, an interesting activity occurs. This activity helps us understand the concept of pressure and its effects on our fingers. Let's delve into the details of this activity and its implications.

Pain and Mark:
When the pencil is pressed between the index fingers of both hands, the pain is felt in the finger that is closer to the sharpened end of the pencil. Additionally, the mark left by the pencil is deeper on the finger that is closer to the sharpened end.

Explanation:
The reason behind this phenomenon lies in the concept of pressure. Pressure is defined as the force applied per unit area. When we press the pencil between our fingers, the force is distributed over the surface area of the fingers that come in contact with the pencil.

Pressure Distribution:
The pressure distribution is not uniform across the entire surface area of the fingers. The pressure is higher at the point of contact with the pencil and gradually decreases towards the edges of the fingers.

Sharpened End:
The sharpened end of the pencil has a smaller surface area compared to the blunt end. This means that the force is concentrated over a smaller area when the sharpened end comes in contact with the finger.

Pain Perception:
Our fingers have numerous nerve endings that are responsible for detecting and transmitting pain signals to the brain. When the pressure is concentrated over a smaller area, the nerve endings in that area are subjected to a higher force per unit area. As a result, we perceive pain in the finger that is closer to the sharpened end of the pencil.

Mark Depth:
Similarly, the mark left by the pencil is deeper on the finger closer to the sharpened end because the force is concentrated over a smaller area. The sharpened end penetrates the skin more easily, leaving a deeper mark compared to the blunt end.

Understanding the Activity:
This activity helps us understand the concepts of pressure distribution, pain perception, and the effect of surface area on pressure. It demonstrates how an object with a smaller surface area can exert a higher pressure when the force is constant. Additionally, it highlights the sensitivity of our nerve endings in detecting and transmitting pain signals.

Conclusion:
By sharpening a pencil at one end and pressing it between the index fingers of both hands, we can observe the differences in pain perception and mark depth. This activity provides insights into the concepts of pressure, surface area, and pain perception, helping us understand the physical properties and sensations associated with such interactions.