Can Wearing a Kevlar Helmet Protect You from Falling Bullets?

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Homework Help Overview

The discussion revolves around the potential dangers of falling bullets, particularly in the context of bullets fired into the air from AK-47 rifles. Participants explore the implications of bullet behavior upon descent and the protective capabilities of Kevlar helmets against such bullets.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants examine the trajectory and terminal velocity of bullets after being fired into the air, questioning the safety of individuals nearby. There is a focus on the effectiveness of Kevlar helmets in protecting against falling bullets, with discussions on the relevant velocities involved.

Discussion Status

The discussion includes various perspectives on the lethality of falling bullets and the protective measures that might be effective. Some participants suggest that the helmet could provide adequate protection based on the velocities discussed, while others raise concerns about the bullet's trajectory and potential danger.

Contextual Notes

Participants reference the muzzle velocity of an AK-47 and the protective limits of modern Kevlar helmets, noting the influence of air resistance on the bullet's speed upon descent. There is an acknowledgment of the need for further exploration of these factors.

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Homework Statement



Part 1:
We have all seen news footage from the Middle East in particular, where heavily armed gunmen toting AK-47 assault rifles fire their weapons into the air. What happens to the bullet after the trigger is squeezed? Can it be dangerous for people nearby when the bullet comes back down?

Part 2:
Assume the bullet is gyroscopically stable. Would wearing a modern army Kevlar helmet protect you?


I have found out that the muzzle velocity on an AK-47 is around 710m/s and a Modern Kevlar Helmet can handle up to 610m/s.
 
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1337 said:

Homework Statement



Part 1:
We have all seen news footage from the Middle East in particular, where heavily armed gunmen toting AK-47 assault rifles fire their weapons into the air. What happens to the bullet after the trigger is squeezed?
Unless it hits a duck, what goes up, must come down, somewhere.
Can it be dangerous for people nearby when the bullet comes back down?
Yes, it could be. In a rare case, it could cause death. The terminal velocity of a bullet can, unlike the low terminal velocity of a falling coin, be surprisingly rather high.

Part 2:
Assume the bullet is gyroscopically stable. Would wearing a modern army Kevlar helmet protect you?
Yes. Just don't look up.


I have found out that the muzzle velocity on an AK-47 is around 710m/s and a Modern Kevlar Helmet can handle up to 610m/s.
Due to air resistance, the speed of the bullet upon return must be less than 710m/s, a lot less. That helmet should, I would think, easily handle it, if your data is correct.
 
If the bullet keeps its trajectory it could be just as lethal. If it does not, then it will be limited to its terminal velocity and probably not lethal.

CS
 
Funny to suggest this here, but...

Check out Myth Busters. They had a show on this very myth.