So here’s the situation, you have two hand grenades at a poolside with their pins out and ready to explode. One is placed on the deck and the other inside the pool. So what is it going to be? Are you going to jump inside the pool or stay on the deck? Youtubers Mark Rober and TheBackyardScientist explored the science behind it, and frankly, it is quite intriguing to say the least.
A grenade has a waffle shaped body, which provides stress concentration points making it easier to break off and disperse when the explosives inside the grenade kick in. These waffle blocks then shoot off in all directions, meaning 40 of them on a standard grenade are 40 potential bullets, making the grenade so deadly.
We all know that a bullet shot inside a water body simply refuses to move more than a few feet, as the fluid drag retards its speed and breaks the momentum. So, by this theory, it seems obvious that if you dive into a pool with a grenade in it, there is a lesser chance of the 40 bullets reaching you.
But there’s a twist!
We know that air is compressible, and water is an incompressible liquid in comparison. So when a grenade, or any explosive bursts in open air, the air around it compresses and takes a lot of energy out of the shockwave, limiting the effect of the shock wave to mere feets. But that will not be the case in a water body, as the incompressible liquid will transfer the energy without much change. This means that when the shockwave reaches a person inside the water, it will exert fatal pressure on the air inside the body, such as in ears, sinuses and the lungs, possibly bursting them and leading to instant death.
So what’s the remedy? As the Youtubers suggest, the best bet it to run off at least 15 feet away from the grenade, and lie down on the floor with feet facing the explosive. This way you have 1% chance of the flying bullets to hit you, while no major effects of shockwaves threatening you.
Have any other theories on this concept?