Discussion in 'Off Topic [BG]' started by yoshi, May 19, 2003.

1. ### yoshi

Jul 12, 2002
England, London
Hi, I had this thought last night for some reason;

Say a bullet moves at 100 metres per second. Someone shoots at you, so you run in the oppostie direction at 99 metres per second. You manage to keep just ahead of it for a split second, at which point it hits you in your back at 100mps but at your relative speed of 1mps, how much damage would it do?

(Ignore any picky facts such as you cant run at 99mps etc).

2. ### yoshi

Jul 12, 2002
England, London
No, does it go over a similar thing?

The thing about your view of 'it does the same damage' is that its moving at 1metre per second in relation to the escapee, so would a bullet moving at 1mps do all that much damage (shoudlve scaled down the speeds a bit more really)?

3. ### wulf

Apr 11, 2002
Oxford, UK
At a relative velocity of 1 m/s, I suspect a bullet would do relatively little damage - your skin would probably be enough to reduce the velocity to zero without giving you much of a bruise.

However, I'm not volunteering to participate in testing...

Wulf

4. ### moley

Sep 5, 2002
Hampshire, UK
Yes, I believe it would be as if you were still, and the bullet hit you at 1 m/s. So you might get a bruise, but no real damage.

5. ### Zon Bass

Jan 20, 2002
Dallas, TX
If you could run that fast, why wouldn't you just step out of the way?

6. ### khay0s

Dec 21, 2002
Brisbane, Australia.

Another vote for a 1 m/s bruise. That'd still hurt, it just wouldn't kill ya.

7. ### DigMe

Aug 10, 2002
Waco, TX
Well seeing as the bullet is only moving at 100mps I'd say that's probably a rubber band gun, thus, no damage done.

8. ### tufnuts

100mps is about 255 MPH. So, 1mps is about 2.5 MPH. You'll be fine, tired...but fine

9. ### BehindTheMoon

If they made the bullet out of light, it would still hit you at c no matter how fast you travelled. However, you could reduce the damage by going relativistic - the photon wavelength (and energy) would be reduced.

No two ways around it - kinetic energy transfer is done on a relative basis. Small relative KE, small damage.

Another thought - the damage done by the bullet is caused entirely by the acceleration of the flesh caused by KE transfer - if you accelerated up to 99 m.s^-1 quickly enough, you would still get acceleration damaged, just not by the bullet.

Nice family thread thing we got going here.

10. ### Only

Sep 8, 2002
Warrensburg, MO
If all the physics get confusing, just think of this in terms of cars. If you're in a parked car and someone else's car slams into you at 100 mph, there will be some serious damage. But if you're going 99, and someone is coming from behind at 100, they'll tap you, but not cause much damage.

11. ### Justin V

Dec 27, 2000
Alameda, CA
No, but wouldn't they send you out of control crashing into something.

12. ### Petebass

Dec 22, 2002
QLD Australia
They would??Remind me never to lend you my car. Are you one of those Volvo drivers that taps another car while attempting to park, then spends the next 20 years telling everyone how safe Volvo's are safety features saved your life. It's 1mph.... you'd barely feel it.

13. ### Bob ClaytonModeratorStaff MemberSupporting Member

Aug 14, 2001
Philly Suburbs
if you could run that fast...join the olympics...

bp13

14. ### yoshi

Jul 12, 2002
England, London
To whom it applies:

15. ### wulf

Apr 11, 2002
Oxford, UK
How far would the bullet travel before crashing to earth? How much of a headstart would you need to avoid the bullet altogether (assuming you can maintain your speed, whereas the bullet is gradually slowed by air resistance and finally thwarted by gravity)?

Wulf

16. ### Gunnar ÞórGuest

Sep 23, 2001
Hafnarfjordur, Iceland
Well in this case if the bullet was launched from a height of 1.7 metres (seems reasonable) it would go 59 metres before it hit the ground, which would be after 0.59 seconds. Since it gains 1 metre per second it would be enough that you started a mere 60 centimetres before it.

17. ### Bob ClaytonModeratorStaff MemberSupporting Member

Aug 14, 2001
Philly Suburbs
this thread is getting too complicated for me...

bp13

18. ### Wrong RobotGuest

Apr 8, 2002
Woah! weird...I had the exact same thought the other night too!

rock on.

19. ### parrott

Dec 2, 2001
Edinburgh, Scotland
Really? I'm finding it quite interesting. I just wish people (well, Gunnar) would show their workings.

20. ### Wrong RobotGuest

Apr 8, 2002
Yeah this is a neat thread.

I have often wondered about how far bullets travel, and what their rate of deceleration is. But I'm not a physics guy, so I don't know

I am really interested in physics, I just never took the class.