Coin sliding on a table slides across an expanding fabric tape

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SUMMARY

The discussion focuses on calculating the exit velocity of a coin sliding on a table covered with an expanding fabric tape. It emphasizes the need to subtract the initial velocity of the coin relative to the ribbon to determine its velocity upon entry. To find the exit velocity relative to the table, the velocity of the ribbon must be added back to the calculated value. This method ensures accurate velocity measurements in dynamic systems involving moving surfaces.

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  • Familiarity with relative velocity calculations.
  • Knowledge of fabric tape dynamics and its expansion properties.
  • Basic mathematical skills for velocity addition and subtraction.
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why is the vector v subtracted at the beginning of the movement, and added at the departure from the fabric? I mean, it's clear why we're subtracting, but the fabric has already been transferred... An impulse? then why are we subtracting?
(the original is in Russian so Fтр is the power of friction, u отн is relative speed and u к is final speed)
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idk
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It is subtracted at the start to find the velocity relative to the ribbon on entry so that the exit velocity relative to the ribbon can be calculated. But to equate that to the given exit velocity, we have to get it back to being relative to the table. To do that we must add the velocity of the ribbon.
 
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