# Crime scene riddle

1. Jun 29, 2006

### fargoth

ok, the story goes like this:
a men was shot, one bullet killed him and the other missed him and got stuck into a heavy wooden chair (about 20Kg).
the bullet made it 4cm into the chair, and the chair was pushed 6cm away by the 5 grams bullet (there were dragging marks on the wooden floor from the chair).

a suspect was caught with a gun, it had a 350m/sec nozzle velocity, and a 26 barrel length.

can you tell if this gun could be the one used in the crime scene from all the information you gathered so far?

Last edited: Jun 29, 2006
2. Jun 29, 2006

### Danger

Sure... dig the slugs out and do a ballistics comparison. If you mean in the mathematical sense from the numbers that you posted, I don't think so. You'd need to know what weight of slug the gun uses to determine the muzzle energy and compare it to that used to move the chair. The barrel length is irrelevant.

3. Jun 29, 2006

### Rach3

This is blatantly a homework question, which belongs in that subforum. You shouldn't misrepresent it otherwise.

What steps have you already taken - how much have you reasoned out so far?

4. Jun 29, 2006

### Cyrus

Only Gil Grissom could answer that, duh.

5. Jun 29, 2006

### Danger

Are you sure? He's a 3rd year undergrad. They wouldn't have something like that for homework, would they.

6. Jun 29, 2006

### Rach3

I'm not sure they wouldn't, the undergrad programs have for some time been sliding backwards (without friction).

7. Jun 30, 2006

### fargoth

i know there are parts that are irrelevant - thats for making it harder...

and as for this being homework - it's not.
it's a riddle ive found, but i think it's broken - i too thought of energy camparisson, but it seems some important figures (such as the friction constant between the floor and the chair) are missing...
does anyone still have homework in this time of year? i thought everyone are having their exams now...

or that it's just a god riddle that i haven't managed to solve... thats why i posterd it here, to see if anyone does better then i.

oh, and by the way, two weeks from now i won't be undergrad anymore =)

Last edited: Jun 30, 2006
8. Jun 30, 2006

### Anttech

Well danger gave you the answer to the riddle

9. Jun 30, 2006

### fargoth

yeah, well, if danger solved it, then i solved it too before i posted it
i just think the one who wrote it had something else on his mind... (or maybe he just forgot to mention things, and it really was a VERY easy riddle...)

Last edited: Jun 30, 2006
10. Jun 30, 2006

### Jimmy Snyder

I've heard this one before. A single bullet killed the man and wounded another guy before falling undamaged to the floor. The bullet that imbedded itself in the chair was fired by a conspirator. The suspect was a patsy and the gun could never have fired the shots because there wasn't enough time.

11. Jun 30, 2006

### Danger

I first started to mention that one, but it occurred to me that you can work it out from the weight of the chair vs. the speed and weight of the bullet, and how far the chair moved.

Congrats!

12. Jun 30, 2006

### Gokul43201

Staff Emeritus
It's not as easy a calculation as it may appear. I spent a minute thinking about it and gave up. It'll take me much longer to figure out.

PS : This is essentially the objective of the problem - to determine the friction coefficient and see if it comes out to be some reasonable number. If not, the crime scene has been tampered with or set up.

13. Jun 30, 2006

### Tom Mattson

Staff Emeritus
Here's a much less challenging one. A man was found stabbed to death. All that was found at the crime scene was the corpse, a puddle of blood, and a puddle of water. The detective claims that he can figure out the murder weapon from that information alone. What do you think it was?

14. Jun 30, 2006

### Danger

Obviously an icicle...........................................................................................

15. Jun 30, 2006

### Tom Mattson

Staff Emeritus
That's some nice sleuthing there.

16. Jun 30, 2006

### arildno

A chihuahua.
It wet itself when it was stabbed into the man.

17. Jun 30, 2006

### Tom Mattson

Staff Emeritus
Chihuauas pee water??

18. Jun 30, 2006

### arildno

I think so.

19. Jun 30, 2006

### Danger

Thanks. It's my weird-weapons background.

20. Jun 30, 2006

### Jimmy Snyder

Here's a variation. A person is found hanged in a room locked from the inside and no other person in the room. There is no object in the room that the victim could have stood upon in order to get the hanging started. A pool of water is found under the victim.