Physics Homework

Question

What is the pressure exerted at the bottom of a rectangular tank with dimensions 100 feet by 100 feet filled to the 40 foot mark with a fluid of SG = 2.5?

Answer 1

Specific gravity refers to the density of a substance compared to the density of water. Since the density of water is given as 62.4 lbs / ft³. The density of the fluid is 2.5 x 62.4 = 156 lbs / ft³. There are 100 x 100 x 40 = 400000 ft³ of the fluid in the tank, so the total weight of the fluid is 400000 x 156 = 6.24 x 10⁷ lbs of fluid in the tank.

Pressure is defined as force / area. Since the density is given as pounds, we then divide the total weight of the water in pounds by the area of the bottom of the tank which is 100 x 100 = 10000 ft² to give a pressure of

6.24 x 10⁷ lbs / 10000 ft² = 6.24 x 10³ lbs / ft².

There is also a simple formula to get pressure at a particular depth. It is P = h x d x g where h is height in feet, d is density in mass per cubic feet, and g is the acceleration of gravity 32 ft/s². In this case, since the density is given in pounds (force) , it is not necessary to use the g factor, so the formula is P = h x d.

Let me know if you have any further questions.