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adatesman
Jul 19, 2010, 7:31 PM
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InDaDacks
Jul 19, 2010, 7:49 PM
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Ohh man, I just sprained a brain muscle
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shimanilami
Jul 19, 2010, 8:05 PM
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ANSWER: Jay should cut the rope.
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Carnage
Jul 19, 2010, 8:13 PM
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shimanilami wrote: ANSWER: Jay should cut the rope.
he should cut the rope, but in a way that he can then use the core strands to make a long enough rope to safely lower everyone to the ground.
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clews
Jul 19, 2010, 8:41 PM
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who climbs with a 30m rope?
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adatesman
Jul 19, 2010, 8:43 PM
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moose_droppings
Jul 19, 2010, 8:47 PM
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Jay weighs about 50lb's more than Paul, how the hell is Paul (even frictionless) going to pull Jay up that incline?
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adatesman
Jul 19, 2010, 8:55 PM
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clews
Jul 19, 2010, 9:01 PM
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at a 40% incline much of jay's downward force is reduced
edited due to a brain fart
(This post was edited by clews on Jul 19, 2010, 9:24 PM)
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moose_droppings
Jul 19, 2010, 9:24 PM
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clews wrote: at a 40% incline, less than half of jay's mass is pulling downward. Most of it will be sent horizontally
I kind of figured it had something to do with the frictionless incline, but they must also figure there is no friction in the bend of the rope going over the edge.
Way *over my head*, much like everything.
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clews
Jul 19, 2010, 9:25 PM
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moose_droppings wrote: clews wrote: at a 40% incline, less than half of jay's mass is pulling downward. Most of it will be sent horizontally I kind of figured it had something to do with the frictionless incline, but they must also figure there is no friction in the bend of the rope going over the edge. Way *over my head*, much like everything.
ahhh!! you quoted my stupidity before I could edit it!!
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majid_sabet
Jul 19, 2010, 10:39 PM
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let me figure out the f2-f1 first.
(This post was edited by majid_sabet on Jul 19, 2010, 10:58 PM)
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cruxstacean
Jul 19, 2010, 10:41 PM
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if the slope is so frictionless how did they get up their to begin with???
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bill413
Jul 20, 2010, 12:43 PM
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cruxstacean wrote: if the slope is so frictionless how did they get up their to begin with???
Using the ice axe which was then dropped.
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bustloose
Jul 20, 2010, 2:25 PM
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they are both clearly noobs, with no business being out in the wild on their own, and deserve whatever fate befalls (heh) them. oh, and they should definitely have to pay for the rescue.
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jrathfon
Jul 20, 2010, 3:11 PM
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aiight:
a) T = 976 N, and Paul decks at 6.47 m/s
b) assuming Paul chills before he cuts the rope and Jay is at rest, Jay craters at 20.7 m/s
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jrathfon
Jul 20, 2010, 3:14 PM
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jrathfon wrote: aiight: a) T = 976 N, and Paul decks at 6.47 m/s b) assuming Paul chills before he cuts the rope and Jay is at rest, Jay craters at 20.7 m/s
so:
a) do i win a cookie
b) that's 14.5 and 46.3 mph respectively for all you 'mericans. aka Jay's getting screwed, why would Paul cut the rope? unless he's got some beef.
c) this all assumes they are in a vacuum.
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cruxstacean
Jul 20, 2010, 3:50 PM
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bill413 wrote: cruxstacean wrote: if the slope is so frictionless how did they get up their to begin with??? Using the ice axe which was then dropped.
So ice axes can hold in frictionless ice? this warrants further testing
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majid_sabet
Jul 20, 2010, 4:09 PM
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jrathfon wrote: jrathfon wrote: aiight: a) T = 976 N, and Paul decks at 6.47 m/s b) assuming Paul chills before he cuts the rope and Jay is at rest, Jay craters at 20.7 m/s so: a) do i win a cookie b) that's 14.5 and 46.3 mph respectively for all you 'mericans. aka Jay's getting screwed, why would Paul cut the rope? unless he's got some beef. c) this all assumes they are in a vacuum.
not so fast
how did you get these #s?
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adatesman
Jul 20, 2010, 4:16 PM
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bill413
Jul 20, 2010, 4:30 PM
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cruxstacean wrote: bill413 wrote: cruxstacean wrote: if the slope is so frictionless how did they get up their to begin with??? Using the ice axe which was then dropped. So ice axes can hold in frictionless ice? this warrants further testing
Yes. If they penetrate the surface of the ice and create a hole at an acute angle (or even perpendicular to) the surface, they'll hold by mechanical interlock, not by friction.
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jrathfon
Jul 20, 2010, 6:02 PM
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adatesman wrote: majid_sabet wrote: jrathfon wrote: jrathfon wrote: aiight: a) T = 976 N, and Paul decks at 6.47 m/s b) assuming Paul chills before he cuts the rope and Jay is at rest, Jay craters at 20.7 m/s so: a) do i win a cookie b) that's 14.5 and 46.3 mph respectively for all you 'mericans. aka Jay's getting screwed, why would Paul cut the rope? unless he's got some beef. c) this all assumes they are in a vacuum. not so fast how did you get these #s? Must have had a copy of the Teacher's edition. The Student edition only has answers to the odd-numbered questions in the back. Oh, the book is Physics for Scientists and Engineers, 3rd Edition by Tipler.
Um, no, I have no such thing. I just happen to be an engineer and know how to use sine... and the equations of motion.
p.s. Majid, I'm not going to let you cheat.
but, find the vector of force pulling on the rope from jay's weight, add that to paul's force (hint F=ma), there's your tension. subtract those two values to get the force paul is accelerating toward the ground with. calculate paul's acceleration and plug it into the EOM. voila time it takes paul to crate, thus you can back calculate his final velocity.
now, calculate the length of the slope, knowing it's 25 m tall at a 40deg incline (with sine). subtract 5 m from it, since there is still 5 m of rope left when paul crater's, now that's how far jay will slide. change that back into the vertical he will fall (again sine), since it's a frictionless slope. he will fall at 1G, again since it's a frictionless slope. now you know jay's cratering acceleration, EOM's, voila, dun.
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jrathfon
Jul 20, 2010, 6:04 PM
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bill413 wrote: cruxstacean wrote: bill413 wrote: cruxstacean wrote: if the slope is so frictionless how did they get up their to begin with??? Using the ice axe which was then dropped. So ice axes can hold in frictionless ice? this warrants further testing Yes. If they penetrate the surface of the ice and create a hole at an acute angle (or even perpendicular to) the surface, they'll hold by mechanical interlock, not by friction.
mmmmmmm, you said interlock. is that the same as interlocken, that town in austria?
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