Question

John was given a task of putting up a notice on the notice board of his school. The process involved pinning the notice paper onto the board which was made of wood. He used the following as shown in the figure below. If he was pressing the pin from the broad end, he did not feel any pain on his thumb but when he tried the same thing from the other end; he felt a sharp prickly pain on his thumb. Why did this happen?

• A. The pin was colder at the broader end
• B. The pin was extremely hot at the pointed end
• C. The pin has more surface area at the broader end
• D. The pin had cushion like material at the broader end

Answer 1

The correct option is C The pin has more surface area at the broader end

When John pressed the pin on the broader end, he did not feel any pain but when he pressed on the other end; he felt a sharp prickly pain on his thumb. This happened because of the difference in pressure. Assuming the same force is applied, each case would have different pressure acting on the thumb. In the first diagram, the thumb pushes on a large area, so the force is spread out and the pressure is low. In the second diagram, the force is concentrated on a smaller area so the pressure is much higher. If a force is applied over a small surface area, john experiences a larger pressure there.