The bottom of a dam is made thicker than the top of the dam. The necessity of having a thick bottom is due to the presence of 

The correct answer is option 2) i.e. ​the depth of the water behind the dam

CONCEPT:

• Pressure: Pressure is the perpendicular force (F) acting per unit area (A). It is given by

Pressure, \(P = \frac{F}{A}\)

• The SI unit pf pressure is the pascal (Pa).
• In fluids, the pressure is related to the density ρ of the fluid as

\(P = \frac{F}{A} = \frac{mg}{A} \times \frac{h}{h} = \frac{m}{V} gh = ρ gh\)

Where h is the height of the fluid column and g is the acceleration due to gravity.

EXPLANATION:

• The pressure applied to the walls of the dam is dependent on the amount of water that is present over the point of the wall.
• Since pressure P ∝ h, the pressure experienced will be more at the bottom of the dam.
• Hence, in order to withstand this pressure, the bottom of the dam is made thicker.
• Therefore, the depth of the water is the reason why dams are made thicker at the bottom.