# Homework Help: Force, pressure and acceleration

1. Dec 7, 2011

### quark001

Our high school physics course recently covered pressure. I invented the following scenario to illustrate something I don't understand about pressure.

Say you have 2 thumbtacks/pins. They have the same mass. You press each pin to a wall with the same force, but only the one with the thin point moves and slides into a crack in the wall that it has created. So only that pin accelerated. F = m.a, so if F and m are the same for both pins, how come a isn't?

2. Dec 7, 2011

### Anyiam

well friend the reason is; the thin pin exerts a greater pressure, beacuse of it small base area as compared with the "thick" pin. Hence, it waz able 2 cause a wreckage through wall by ur applied force, which inturn producd d motion!
Generally, the pressure created by a certain force "F" is inversly proportional to d area in contact.

3. Dec 7, 2011

### JHamm

Normal force, the one that didn't move had a force on it from the wall whereas the one which did move wasn't actually pressing right up against the wall since it was sliding into a crack so the wall wasn't pushing back as much.

4. Dec 7, 2011