How do you calculate the additional pressure needed to overcome gravity for a fire on the tenth floor?

To determine the additional pressure needed to overcome gravity for a fire on the tenth floor, it's essential to understand the basic principle of how water pressure decreases in a vertical column due to gravity. Water pressure drops approximately 0.433 psi for every foot of elevation gain.

In a building, each floor usually represents about 10 feet of height. Therefore, to calculate the pressure required to reach the tenth floor, you would first need to account for the total height of that floor from the ground.

Since the ten floors amount to about 100 feet, we can use the following approach:

1. Recognize that you need to overcome the gravitational pull on water to deliver it effectively to the fire on the tenth floor.

2. For every floor (10 feet), you would estimate the necessary pressure increase needed.

3. Considering the total number of floors (10), the calculation method of subtracting 1 from the total floors before multiplying by 5 reflects an understanding that the calculation should not include the bottom floor (which does not require overcoming elevation).

This calculation—(10 - 1) x 5—effectively yields:

• 9 x 5 = 45 psi.

Thus, the correct way to calculate the additional pressure to overcome gravity