why are water tanks broader at the bottom than at the top
Water tanks are broader at the bottom than at the top to provide stability and prevent tipping over. The broader base of the tank creates a larger surface area in contact with the ground, distributing the weight of the water more evenly. This design helps to lower the center of gravity, making the tank more stable and less likely to tip or topple.
To understand why this design is effective, you can consider the concept of center of mass. The center of mass is the point where the entire weight of an object is considered to be concentrated. When an object is in equilibrium, the center of mass is directly above the base of support.
In the case of a water tank, the weight of the water inside creates a downward force that must be balanced by an upward force exerted by the ground. The broader base of the tank increases the distance between the center of mass and the edge, thus increasing stability. This is because a larger lever arm (the distance between the center of mass and the point of support) makes it harder for an external force to overcome the tank's stability.
So the broader bottom of water tanks is intentionally designed to maximize stability and ensure that the tank remains upright, even when it is filled with a large amount of water.