183_notes:examples:a_yo-yo

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183_notes:examples:a_yo-yo [2014/10/31 16:22] – pwirving183_notes:examples:a_yo-yo [2014/11/06 02:40] – pwirving
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 === Assumptions and Approximations === === Assumptions and Approximations ===
 +
 +You are able to maintain constant force when pulling up on yo-yo
 +
 +Assume no slipping of string around the axle. Spindle turns the same amount as string that has unravelled
 +
 +No wobble included
 +
 +String has no mass
 +
  
 === Lacking === === Lacking ===
 +
 +Change in translational kinetic energy of the yo-yo
 +
 +Change in the rotational kinetic energy of the yo-yo
  
 === Representations === === Representations ===
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 Surroundings: Earth and hand Surroundings: Earth and hand
 +
 +{{course_planning:course_notes:mi3e_09-034.jpg?100|}}
  
 b:  b: 
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 Surroundings: Earth and hand Surroundings: Earth and hand
 +
 +{{course_planning:course_notes:mi3e_09-035.jpg?100|}}
 +
 +$\int_i^f \vec{F}_{net} \cdot d\vec{r}_{cm}$
  
 === Solution === === Solution ===
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 From the Energy Principle (point particle only has $K_{trans}$): From the Energy Principle (point particle only has $K_{trans}$):
  
-$\DeltaK_{trans} = (F - mg)\Deltay_{CM}$+$\Delta K_{trans} = (F - mg)\Delta y_{CM}$ 
 + 
 +$\Delta y_{CM} = -h (from\; digram)$ 
 + 
 +$\Delta K_{trans} = (F - mg)(-h) = (mg - F)h$ 
 + 
 + 
 +b:  
 + 
 +$\Delta E_{sys} = W_{hand} + W_{Earth}$ 
 + 
 +$\Delta K_{trans} + \Delta K_{rot} = Fd + (-mg)(-h)$ 
 + 
 +$\Delta K_{trans} = (mg - F)h$ (From part (a)) 
 + 
 +$(mg - F)h + \Delta K_{rot} = Fd + mgh$ 
 + 
 +$\Delta K_{rot} = F(d + h)$ 
  
  
  
  • 183_notes/examples/a_yo-yo.txt
  • Last modified: 2014/11/06 02:59
  • by pwirving