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  Homewood Fire Chief Bob Grabowski helps 
  Kristina Sales of Glenwood get hands-on 
  experience with a fire hose at a PopUp 
  Science session on Sept. 23.
(Photos by 
  Eric Crump)

Fighting a fire with algebra?

Teens at the Homewood Science Center’s “Pump It Up!” PopUp Science program found out just how much math is involved in the work of a firefighter.
On Saturday, Sept. 23, teens got a math lesson from Homewood Fire Chief Bob Grabowski.
  Fire Chief Bob 
  Grabowski helps 
  Nicholas Ramirez 
  of Harvey learn how 
  to bring a fire hose 
  to a hydrant. 


“People always think firemen pull up and they pull a lever and the water comes out,” Grabowski said. “When the guys drive the fire engines and get to the scene, they have to do what’s called fire engineering. There’s a lot of math involved and different calculations.”

Variables include the size of the hose ― 1.75, 2.5, 3 or 5 inches ― the pressure flow, gallons per minute and more.   
With simple equations, he got his students to figure out how the water system works, how the public works department and fire department have to calculate water flow and friction loss. 
Straight stream and fog stream nozzle pressures vary between 50 and 100 pounds per square inch (PSI), the amount of force.  How much water firefighters will use is calculated as gallons per minute (GPM).
The distance the water flows through a hose could be as far as 200 feet. The friction of water moving through the hose is part of the calculation.
“If you set the gauge at 50 and the engine revs up and you get it to 50, it’s a long hose that water’s running through to get to the nozzle,” Grabowski explained. The friction on the hose slows the water down.
“Firefighters, in their minds, have to calculate flows and if it’s a big fire there are a lot of calculations because there’s only so much water available and you have to decide how you’re going to use it,” he told the teens.

He also pointed out that a fire truck is the one with the ladder. A fire engine is the one with the gauges and hoses to fight a fire.

After their lessons in the science center, the group trooped over to the St. Joseph Church parking lot, where a fire engine was set up for demonstrations and some hands-on experience. 

Grabowski and two firefighters showed the students how the water systems on the truck work, and students got to pull hose and hook it up to a hydrant and shoot water across the parking lot.


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