Firefighter harnessing a simple physics concept to put out a massive fire is mind-bending

The material world is bound by the laws of physics. From a house kitchen to a nuclear power plant, physics is present everywhere. Isaac Newton’s laws tell us why things always fall downwards, whereas Albert Einstein’s famous relativity equation proclaims that energy and mass are different forms of the same thing. Another intriguing concept in the realm of physics is “Bernoulli’s principle.” 

A physics teacher, who goes as @wolf_science on TikTok, explained the principle using a cylindrical plastic bag as a metaphor. In a short clip he posted, he was seen standing with a gigantic yellow bag spread out in front of him. “I wonder how many breaths it would take me to fill up this incredibly long plastic bag.” He bet that he could fill up that long bag with just one breath.

He put his lips on the mouth of the bag, pressing its edges with his fingers, and started blowing air inside it. After he had blown 10 long breaths into the deflated bag, he felt exhausted. “Is there perhaps a better way to do this?” he wondered and released all the air from the bag. “And now we’re going to use the ‘Bernoulli’s principle,’” he exclaimed.

“We’re going to blow into the bag but we’re not going to put our mouth right on the bag. What happens there is – as we blow in, surrounding air is pulled in as well to the low-pressure area. This is Bernoulli’s principle,” he elaborated and again moved closer to the bag’s open mouth. But instead of pressing his mouth against its corners, he maintained a little distance between his mouth and the bag’s mouth while blowing the air inside. Interestingly, the long tube inflated into a balloon in an instant.

While describing the concept, the teacher also revealed an astounding fact. He said that firefighters also employ this principle from time to time. And he is right. As it turns out, Bernoulli’s principle is extensively used by firefighters in putting out the fire. @unlimitedknowledge18 explained this connection in a TikTok video. The clip displayed a house getting smothered by fiery orange flames. A firefighter came to the rescue and placed a water hose pipe in front of the house door, from where the fire was oozing out. But instead of positioning the pipe’s mouth toward the interior of the house, he positioned it towards the opposite side, and the squirt of water shot launched outdoors. This might appear uncanny, but people in the comments said that it is a great method to remove smoke from the burning area.

Bernoulli’s principle is based on the branch of physics called “fluid dynamics” or “hydrodynamics,” a study of the equilibrium, pressure, and velocity of fluids. According to Boston University, Bernoulli’s principle states that “as the velocity of fluid flow increases, its pressure decreases.” Writing about Bernoulli's principle, Matt Hinkle of Box Alarm Training said, "Water flowing from a nozzle will create an area of low pressure and draw even more air into the area you are directing the stream. This is significant when fighting fires in under-ventilated spaces or flowing water into a structure from the exterior."

Recently, another firefighting footage has been making rounds on social media that shows some firefighters brilliantly using Bernoulli’s principle to put off the fire. This footage was shared by @historyinmemes on X. The post garnered 7 million views and 20,000 likes.

The viral footage shows a tall building with a gabled roof. From the upper story of the building, a gush of fire is spewing out. Down below on the ground, two firefighters are standing in front of a mounted ladder. Soon, they raise the mouth of a pipe onto the upper window. Interestingly, they don’t release the water inside the burning area on the other side of the window. Instead, they turn the mouth of the pipe away, blasting and shooting a jet of water in the opposite direction. 

When the firefighters shoot the jet of water away from the window, it creates a field of low pressure outside the window and high pressure inside the burning area. Since the property of thermodynamics is that air moves from a high-pressure area to a low-pressure area, the air inside the window starts to drift outside. In the process, it also brings an enormous amount of oxygen with it, starving the fire inside of this flammable gas. As the scarcity of oxygen inside the window increases, the fire eventually douses off.