Can Wearing a Kevlar Helmet Protect You from Falling Bullets?

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In summary, the conversation discusses the potential danger of bullets fired into the air from AK-47 assault rifles and whether a modern army Kevlar helmet can protect against them. It is stated that the bullet can be dangerous upon return and that a Kevlar helmet can handle the speed of the bullet, but it is advised not to look up. Additional information about the terminal velocity of the bullet and the show Myth Busters is also mentioned.
  • #1
1337
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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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  • #2
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.
 
  • #3
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
 
  • #4
Funny to suggest this here, but...

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

1. What happens to a bullet fired upwards?

When a bullet is fired upwards, it follows a ballistic trajectory and will eventually reach its peak height before falling back down to the ground due to gravity.

2. How high can a bullet fired upwards go?

The height a bullet can reach when fired upwards depends on factors such as the initial velocity, the mass and shape of the bullet, and air resistance. On average, a bullet fired from a handgun can reach a height of 1-2 kilometers, while a bullet fired from a rifle can reach heights of up to 5 kilometers.

3. Is it safe to fire a bullet upwards?

Firing a bullet upwards is extremely dangerous and should never be done. The bullet can travel long distances and can potentially injure or kill someone when it falls back down. This is why it is important to always follow proper gun safety rules and never fire a gun into the air.

4. Can a bullet fired upwards kill someone when it falls back down?

Yes, a bullet fired upwards can cause severe injury or death when it falls back down. The velocity of the bullet can still be lethal even when it reaches its peak height and begins to slow down due to air resistance.

5. Are there any laws against firing bullets upwards?

Yes, many countries have laws against firing bullets upwards due to the potential danger it poses to public safety. In the United States, it is considered a criminal offense and can result in fines and jail time. It is important to always follow local laws and regulations regarding gun safety.

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