1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Angular Speed Question,

  1. Apr 17, 2006 #1
    Angular Speed Question, Please Help!

    I have this question I am stuck on and I don't understand and need help:

    In a neutron velocity selector, two thin discs of a neutron absorbing material are rigidly mounted on a shaft 1 meter apart and rotated with constant angular speed of 1000 revolutions per minut. There is a slot in each disc and the angular seperation between slots is 3 seconds of arc. What would be the velocity of the neutrons which pass through this system?
     
  2. jcsd
  3. Apr 17, 2006 #2

    Doc Al

    User Avatar

    Staff: Mentor

    3 seconds of arc is what fraction of a revolution? (1 revolution = 360 degrees.)
     
  4. Apr 17, 2006 #3
    I know that 1000 rev/min is about 105 radians/second. The frequency is 16.7 Hz and the time would be 0.0599 seconds. But, I don't know how to find the angle.
     
  5. Apr 17, 2006 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Start by answering my question. Look it up if you have to.
     
  6. Apr 17, 2006 #5
    It would be 50 revolutions every 3 seconds.
     
  7. Apr 17, 2006 #6

    Doc Al

    User Avatar

    Staff: Mentor

    "seconds of arc" is a measure of angle, not time:

    1 revolution = 360 degrees
    1 degree = 60 minutes (of angle)
    1 minute = 60 seconds (of angle)
     
  8. Apr 17, 2006 #7
    So, if one revolution is 360 degrees and 1 degree is 60 minutes, then 3 seconds would be 3 seconds/3600 seconds = 8.333e-4 degrees?
     
  9. Apr 17, 2006 #8
    I dont quite know what formula to use. Is it V= omega x radius or arc length= velocity x time? Do I add the velocity of both discs or is it just on velocity?
     
  10. Apr 18, 2006 #9
    By the time the neutron travels from one disc to the other, the disc should have rotated by 3 seconds.(Here 1 second = 1/3600 degrees.)
    The disc makes 1000 revs. per min. which implies it rotates at the rate of 6000 deg. per sec. i.e. 6000*3600 seconds(angle) per sec.
    Therefore it takes 1/(7200000) secs. to rotate 3 by seconds.In this time it travels 1m.Therefore its velocity is 7200000 m/s.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Angular Speed Question,
  1. Angular speed question (Replies: 3)

  2. Angular Speed question (Replies: 6)

Loading...