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On 11/7/2010 4:59 PM, Carl Mungan wrote:
friction between the ribbon and the prism. If the clamp provides ONLY aAh you are dealing with the consequences of imputing a particular methodWell, I think that's a valiant effort. But not very stable. There is no
of holding the small mass and ribbon. You visualize a stretchable ribbon
(shame on you, this is meant to be a physicist';s ribbon! :-) and
the upward force is I suppose an upslope foce to balance the down slope
gravity vector.
For some reason, I imagined a clamp appling a normal force to the small
mass, so the large block can stretch the ribbon as desired while the
ramps grow more
high-pitched, so to speak.... would that resolve the issue?
Brian W
normal force, it will slip sideways and the block is likely to tilt the
clamp over (I'm imagining it as consisting of a knife edge clamping down on
top of the block) and sneak out. Realistically, I think that the blocks have
to be help by a normal force perpendicular to the lower edge face of the
block. Like a gate that swings open (sideways or upward) as in a ski race.
-Carl
Hmmm...here you are imputing the means by which one applies a force to
render the smaller mass in a comparable situation to the larger mass for
an initial period: no friction between ribbon and ramp, appreciable
static friction between masses and ribbon:
I can visualize a clamp (with a locating peg if you wish?) that applies
a normal force to place the smaller mass in the position of providing
greater normal force hence higher peak friction force to the ribbon
than the larger mass.
It took me a while to visualize your reference to the ribbon rippling up
upslope of both masses. This would be a function of the stiffness of the
ribbon: reminds me that climbers like compliant ropes like nylon for
safety lines, that sudden jerk at a fall becomes manageable: Horse
tethers made of stiffer fibers are preferred
against the panic case, where an end latch lets go. Too much energy
stored in the stretch becomes a missile to bystanders.
Brian W
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