# The bond of roommates

Jesse and I were discussing what would happen if somehow, mid-rock climb, the rope snapped. While this would never happen to a mindful rock climber (because wear on rope is very obvious), we were trying to figure out how quickly the belayer would be able to react and whether or not they could catch or slow the descent of the falling climber.

I commented on how I thought there would certainly be a chance of death for the person trying to save his falling comrade.

mike d: “Especially if I tried to save someone like Joel. I think if he landed on top of me, his weight could easily crush my chest.”
jesse: “I don’t know, I think the chance of survival for the climber would drop significantly, with very little chance of the belayer dying.”
mike d: “it would be easy enough to figure out.”
jesse: “true. we know the mass, the acceleration, and the height… though I don’t know the strength of bone.”
mike d: “well, if it came out to be some ridiculous amount of force…”

AND THEN! SIMULTANEOUSLY…
mike d: “like 12,000 pounds of force.” Jesse: “like 6 tons of force.”

6 TONS = 12,000 Lbs

Weird that we would both choose the same arbitrary “ridiculous amount of force.”
I’ve come up with two possible explanations.

1. Jesse and I have a strange roommate bond that results in us thinking alike… though in different units.
2. a ridiculous amount of force is just about equal to 6 tons.

### 15 thoughts on “The bond of roommates”

• 5/5/2005 at 10:24 am

Thats awesome. Maybe you guys are supposed to be some sort of circus act for nerds.
” See the amazing forceonverting Psychic Twins. Ask them both a question about anything andthey will give you the same answer, but in different units!!! just \$5!! Step right up, step right up!!”

• 5/5/2005 at 11:02 am

Are you sure Jesse didn’t say 6 tons JUST after you said 12,000lbs?

We need to get these facts straight before we can actually think about this whole room mate bond thing.
I also don’t think 6 tons is a ridiculous amount of force, 101 tons maybe….

• 5/5/2005 at 11:17 am

they’ve done the breaking force of bones on good old mythbusters plenty of times.. i can’t recall the numbers off the top of my head though.

anyways, i don’t know how heavy this joel is but if he’s like kurt then i would be concerned about trying to catch him.

we’re talking like 20-30 feet here?
I think that the belayer would probably cushion the climber’s fall by quite a significant amount. Certainly enough to where they’d survive the fall.. and i don’t know that the belayer’s chest would be crushed… unless he’s lying flat on the ground like a mat or something…

that’d be weird.

• 5/5/2005 at 11:57 am

Marian: yes, it was at exactly the same time.

Jon: more like 30-40 feet. And Joel is definitely Kurt-esque. If not more so. He was in the army though, so it’s mostly muscle. He can bench 345 lbs. He’s big.

• 5/5/2005 at 12:27 pm

Would you have enough time to do anything?

Say someone who weighs 200 lbs falls 20 feet, and gravity increases one’s falling speed by a factor of 9.8… meters, I think. (Ok, so let’s change 20 feet to meters — about 7 meters, right?) If I recall high school physics correctly, in terms of time, it doesn’t matter how much something weighs — it falls at the same rate.
7 meters = 1/2 (9.8 x time squared)

OK, so it takes Joel 1.19 seconds to fall. Would that give the belayer enough time to react?

Joel’s velocity is:
v= 9.8 x 1.19
v = 11.662 m/s

I think the force would be 200 x 9.8 = 1960 lbs – closer to one ton.
??

Keep in mind I haven’t taken a physics class in eleven years and I have no idea what I’m talking about. I just thought I’d try my hand at remembering equations and stuff. Shoot me down!!!

• 5/5/2005 at 12:35 pm

There’s always air resistance…but that’s neglible.

Also, nobody else commented on this, but MikeD, you’re eating a bell pepper? How? On something else? Or, like an apple?

• 5/5/2005 at 12:41 pm

I pictured him eating with a knife and fork. I ahve no idea why he’d be eating a raw bell pepper with a knife and fork though. and it’s a steak knife, in my head.

• 5/5/2005 at 12:54 pm

Actually, I was eating slices of green bell pepper. I’m trying to increase the amount of vegetables that I eat on a daily basis.

• 5/5/2005 at 2:16 pm

anytime anyone mentions eating bell peppers, i think of the iron chef guy just chomping down on it.

way to go television

• 5/5/2005 at 2:45 pm

From this I conclude you guys do to much maths

• 5/5/2005 at 3:19 pm

Your ropes had best be in top condition on Saturday in that I do not want to find out how much damage the force of 110lbs smacking onto the floor causes….

• 5/5/2005 at 5:44 pm

nice drawing, mike d! nice shirt too.

• 5/6/2005 at 8:22 am

I think the deciding factor here is kinetic energy, not just force. F=ma, so speed doesn’t even come into play. No matter what, you are going to have 200lbs of force hitting you. That’s what weight is.

E=1/2mv^2. So, the mass is 200 lbs/32 ft/s/s = 6.25 [imperial units for mass] (F=ma so m=F/a). We’ll take Alicia’s time (1.19s), and apply 32 ft/s/s to get a speed of 38.08 ft/s at impact.

E=1/2*6.25*38.08^2= about 4,530 pound-feet, or 6,145 Joules. Google says that this is 1.469 kilocalories. 1 kilocalorie is what nutritionists call a Calorie. So you’re getting hit with the full force of diet coke.

Disclaimer: I’m not even that confident about my maths. But I think having somebody fall on you would be similar to being that person and falling to the ground from the same height. Dig?