kei ignatov is an absolute monster

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Published on November 24, 2021 1:05:42 AM ● Video Link: https://www.youtube.com/watch?v=KJGiQJHumWQ

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How fast do you have to be to punch through a steel door?

Assuming the person is durable enough to not break his hand, how fast would he have to move his fist to punch completely through a solid steel door that is 1 inch thick?

In this idealized case, we can compute an approximation of the necessary velocity of an non-deformable human fist backed up by the entire weight of the unbreakable unbendable human to punch through:

The shear strength of steel is about 350 to 1400 MPa (50,000 to 200,000 psi). Let's assume 1000 MPa. (To get an idea of how much this is, 1000 MPa is about 10,000 atmospheres.)

To punch a neat hole, we must apply enough force to overcome the shear strength of the 25 mm of steel along the circumference of the hole; let's say that the circumference of the fist is about 400mm (it's a big fist but not huge).

400 mm circumference times 25 mm depth is 10,000 square mm, or 0.01 square meters.

0.01 square meters times 1000 megapascal is 10 meganewton. (For a rough idea of bigness, that's about 1000 tons-force.)

10 meganewton of force applied on a 100 kg body (big fist, big man) gives an acceleration of 100,000 meters per second squared.

With a uniform acceleration a, a body will come to rest in a given space S (= the thickness of the door in our case) when it starts with a velocity v=√(2aS). Plugging in the numbers, we find that v=2×100,000×0.025=√(71m/s). That's about 250 km/h or 155 mph.