angular velocity- need help!

• hiphop2009

  29 Jul 07, 16:42

  A majorette in the Rose Bowl Parade tosses a baton into the air with an initial angular velocity of 2.5 rev/s. If the baton undergoes a constant acceleration while airborne of 0.2 rev per second square, and its angular velocity is 0.8 rev/s when the majorette catches it, how many revolutions did it make in the air?
  
  14 rev
  1 rev
  44 rev
  4 rev
  
  choose one.
• darkhour

  29 Jul 07, 16:54

  Originally posted by hiphop2009:

  A majorette in the Rose Bowl Parade tosses a baton into the air with an initial angular velocity of 2.5 rev/s. If the baton undergoes a constant acceleration while airborne of ‑0.2 rev per second square, and its angular velocity is 0.8 rev/s when the majorette catches it, how many revolutions did it make in the air?
  
  14 rev
  1 rev
  44 rev
  4 rev
  
  choose one.

  ur qn got problem anot?if its accelerating at 0.2rev per second square, how can the final velocity b lower than the intial velocity?
• eagle

  29 Jul 07, 17:03

  I think you mean deceleration of 0.2 rev/s
  
  remember in linear mechanics
  
  v^2 = u^2 + 2as
  
  in angular mechanics, the formula to be used is analogous
  ie
  
  (final angular velocity)^2 = (initial angular velocity)^2 + 2 * (acceleration) * (revolutions)
  
  so,
  
  0.8^2 = 2.5^2 + 2 (-0.2) (rev)
  resolving,
  rev = 14 revolutions
• hiphop2009

  29 Jul 07, 17:04

  Originally posted by eagle:

  I think you mean deceleration of 0.2 rev/s
  
  remember in linear mechanics
  
  v^2 = u^2 + 2as
  
  in angular mechanics, the formula to be used is analogous
  ie
  
  (final angular velocity)^2 = (initial angular velocity)^2 + 2 * (acceleration) * (revolutions)
  
  so,
  
  0.8^2 = 2.5^2 + 2 (-0.2) (rev)
  resolving,
  rev = 14 revolutions

  ooooo. thanx!. hehe~