Answer the following with reference to the physical quantity pressure.
(i) Define pressure and write the mathematical relation connecting pressure, normal force and area.
(ii) State the SI unit of pressure and express it in base units of mass, length and time.
(iii) Derive the dimensional formula of pressure.
(iv) Give one practical situation in which a small contact area is desirable and one in which a large contact area is preferable. State clearly how the area chosen affects the pressure in each case.