Which weight will lift first as the rope is pulled?
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Which weight will lift first as the rope is pulled?
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Re: Which weight will lift first as the rope is pulled?
#2If the system is frictionless, the rope is weightless, and the weights are not supported, then the lighter weight will rise and the heavier weight(s) will fall. Therefore if the rope is pulled very slowly, the lighter weight will rise first.
If the rope really is weightless and the pulleys really are fictionless (and inertialess) then it doesn't matter how hard or fast you pull, the lighter weight will rise first. This is at odds with your intuition simply because you have no (or insufficient) experience with weightless and frictionless environments. This is one reason why space is so bloody dangerous, in addition to the dangers posed by, say, diving, where similarly to space, your equipment has to work perfectly or you die.
In the real world, pulling fast enough will make the closer weight rise first.
The truth lies somewhere in between.
Re: Which weight will lift first as the rope is pulled?
#3Well, the diagram is impossible unless the weights are all resting on the floor, so let's assume they are. This system will find a steady state only at a local minimum of potential energy, so the lightest weight will be lifted before the heavier two get off the ground.
Re: Which weight will lift first as the rope is pulled?
#4If the system is frictionless, the rope is weightless, and the weights are not supported, then the lighter weight will rise and the heavier weight(s) will fall. Therefore if the rope is pulled very slowly, the lighter weight will rise first. If the rope really is weightless and the pulleys really are fictionless (and inertialess) then it doesn't matter how hard or fast you pull, the lighter weight will rise first. Th…
In the real world, the heavier weight lifts first -- assuming that you can set up a bunch of high friction non-pulleys:
http://gbxforums.gearboxsoftware.com/showthread.php?t=59835&...
Re: Which weight will lift first as the rope is pulled?
#5Its not a static system; the question is unfair.
Re: Which weight will lift first as the rope is pulled?
#6If the system is frictionless, the rope is weightless, and the weights are not supported, then the lighter weight will rise and the heavier weight(s) will fall. Therefore if the rope is pulled very slowly, the lighter weight will rise first. If the rope really is weightless and the pulleys really are fictionless (and inertialess) then it doesn't matter how hard or fast you pull, the lighter weight will rise first. Th…
In the real world, the heavier weight lifts first -- assuming that you can set up a bunch of high friction non-pulleys: http://gbxforums.gearboxsoftware.com/showthread.php?t=59835&...
That happens because of friction, though. If there's over 20 lbs of friction on each 'pulley', the weight in front will be lifted first.
Re: Which weight will lift first as the rope is pulled?
#7Well, the diagram is impossible unless the weights are all resting on the floor, so let's assume they are. This system will find a steady state only at a local minimum of potential energy, so the lightest weight will be lifted before the heavier two get off the ground.
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Re: Which weight will lift first as the rope is pulled?
#8[deleted]
Re: Which weight will lift first as the rope is pulled?
#9Its not a static system; the question is unfair.
Why does that make it unfair?
Re: Which weight will lift first as the rope is pulled?
#10None. Instead he'll pull the ceiling down as they failed to screw it into the studs. ;-)