They make it look so easy in action films, but there’s actually a lot of science that goes into kicking a door open. As this dog is finding out!


children and dog kicking door


Now, this may seem like a harsh subject but my business partner Paul attended many forced door Burglaries and also had to force open a few doors himself during his 17 years police service. With this in mind, I feel that it is important for you to understand the science behind forcing doors open before we can fully appreciate the importance of home security.


While it’s not as widely studied as medicine or physics, the science of smashing open a locked door with a swift kick is an important one to certain careers. As an agent in the DEA (Drug Enforcement Agency) in the US for well over two decades, Mike McDaniel was trained in the science of kicking down doors at the FBI academy in Quantico.


Today, the FBI academy doesn’t place as much emphasis on kicking doors open, opting for battering rams instead. However, battering rams don’t always work (as this team of police from Turkey learned the hard way) and McDaniel insists that a swift, front-facing kick is still the best way to open certain kinds of door. So what advice does he have? And what’s the science behind it?


The Sound of a Broken Sash Lock


Listening is a big part of kicking open a door. McDaniel claims that reinforced doors make a dull thud and, if you hear this, it’s time to get the battering ram. What you’re listening for is the sound of the sash lock cracking straight through the door frame. When a frame is made of flimsy wood, or when the lock isn’t securely installed, kicking down this kind of door is easy enough. When it’s not, then it’s best to save your energy.


broken door handle and lock


Physics can explain why you hear a thud when a door is reinforced and a louder crack when a door is about to break open. Sound waves are caused by displacement of molecules. The more that molecules are displaced, the louder the sound. With a reinforced door, your kick isn’t going to displace many molecules, so all you get is a dull thud for your efforts. Meanwhile, the molecules in a door with a wooden frame can be hugely displaced by the same kick. As a result, you get a satisfyingly loud crack as the door crashes open.


To avoid this, we’d recommend strong sash locks and door bolts. However, there are techniques for kicking down bolted doors, too.


Bolts Vs. Boots: Can You Kick Open a Bolted Door?


It depends. The idea of a bolt is to make a door more secure than a lock would by being longer, thicker and stronger than locks are. The deeper the bolt is allowed to be, the stronger the door. This kind of reinforcement is also a common principle in bridge and building engineering. It’s helped to save countless engineering projects from disaster after years of learning the hard way.


The best way to kick open a door with a bolt is to kick right above where the bolt and the sash lock are. Once again, though, if you don’t start to hear that cracking sound, then you’re probably out of luck. If the bolts are spread out (one near the top, one near the bottom, with a lock in the middle) this even distribution of force will make the door even harder to kick open.


Speaking of even distribution of force…


The Science of Weight Distribution


When kicking open a door, McDaniel recommends making sure that your foot strikes the door completely flat. The reason for this is weight distribution. If you were to kick with the force needed to break open a door and strike the door heel first, you’d end up directing all that force onto a small section of your foot. This means you’d likely end up breaking it — your foot, not the door. By spreading the force out with a flat foot, you are protecting your body.


The physics of weight distribution is part of what makes doors easier to kick down. However, this same principle can be also applied to lessening the impact of your weight so that you can walk on eggs without breaking them.


Safety Considerations


shoes in front of safety first sign


Finally, it’s worth bearing certain safety considerations in mind. McDaniel says that the temptation can be to try bashing the door open with your shoulder. In terms of weight distribution, this actually makes more sense than using your foot. However, he recommends against this. Your shoulder is a softer, less powerful part of your body than your foot. As a result, trying to break open a door in this way can cause many injuries.


Finally, McDaniel recommends covering your legs with jeans or trousers (as opposed to shorts) to save yourself from splinters. And don’t forget to stretch as well!


If you want a door which can withstand more than a swift kick, check out our range of sash locks and bolts. Or as always feel free to call and speak to me or Paul for advice. Remember if you spend over £45, we can even deliver your order for FREE.