1. Limited time only! Sign up for a free 30min personal 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!

How to find angle from angular velocity?

  1. Apr 10, 2013 #1
    A cat swipes at a spool of thread, which then rolls across thefloor with an initial speed of 1.5 m/s. The spool deceleratesuniformly to a stop 3 m from its initial position. The spool has aradius of 1.5 cm and rolls without slipping.


    a) What is the initial angular velocity?
    1.5 /(1.5/100)=100 rad/s


    b) Through what total angle does the spool rotate whileslowing to a stop?
    c) What is the angular acceleration during this motion?

    I dont really know how to do the rest of the parts.
     
  2. jcsd
  3. Apr 10, 2013 #2
    For b) what is the circumference of the spool? How far did it go?
     
  4. Apr 10, 2013 #3
    For part b, we are given that the spool travels 3m. The spool rolls along its circumference, right? How many circumferences in 3m? (And how many radians in one circumference)?
     
  5. Apr 10, 2013 #4

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    a. this is correct - you used vT=rw ... but do you know why this is the case?

    b. Get something round and roll it back and forth across a flat surface.
    Watch carefully.

    What is the relationship between the distance rolled and the amount the object turns?

    c. How would you find regular acceleration?
    Relationship between the linear acceleration of the edge of the ball and it's angular acceleration is...
     
  6. Apr 10, 2013 #5
    the circumference is 0.094 m, and it traveled 3 m

    there 95.74 circumferences in 3 m
     
  7. Apr 10, 2013 #6
    I got the same circumference, but found a different number of circumferences in 3m. How did you calculate 95.74?

    Once you have the # of circumferences, you can use the # of radians in one circumference to find the total angle.
     
  8. Apr 10, 2013 #7
    3/0.094=95.74
    should it have been smaller?
     
  9. Apr 10, 2013 #8
    3/0.094 isn't 95.74. Are you making a typo somewhere?
     
  10. Apr 10, 2013 #9
    I must have had the wrong numbers some how.
    my new answer is 31.91
     
  11. Apr 10, 2013 #10
    Yes, and how many radians in each circumference?
     
  12. Apr 10, 2013 #11
    i did 31.91/1.5=21.27 rad.
     
  13. Apr 10, 2013 #12
    Aren't there 2pi radians per circumference?
     
  14. Apr 10, 2013 #13
    31.91/(2pi)=5.07
     
  15. Apr 10, 2013 #14
    Other way around. If you have 31.91 circumferences, and 2pi radians/circumference, then you can just multiply.
     
  16. Apr 10, 2013 #15
    31.91*2pi=200.4
     
  17. Apr 10, 2013 #16
    Yes, though if you used unrounded numbers, you'd get exactly 200.
     
  18. Apr 10, 2013 #17
    so 200 would be the total angle rotated?
     
  19. Apr 10, 2013 #18
    In radians, yeah.
     
  20. Apr 10, 2013 #19
    for part c I know how to solve if there was an extra time given .
    would I find time by 3/1.5=2

    200/2^2=50 to get the answer?
     
  21. Apr 11, 2013 #20
    would the equation Ø = w1 t + 1/2 ã t^2 be applied where

    Ø - angular displacement
    w1 - initial angular velocity
    t - time
    ã - angular acceleration
    ??
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: How to find angle from angular velocity?
Loading...