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!

Oscillator Questions

  1. Jul 4, 2011 #1
    The position of the center of the box shown is given by the equation:
    x = 4.4 m * cos(29/sec * t)

    (a) What is the position of the box 2 seconds after the oscillations have started?
    x = m
    I dont know how to start A. I plugged in 2 seconds for t in the above equation, but my answer is not right.

    (b) What is the amplitude of the box's oscillations?
    The amplitude is 4.4 and it's correct.

    (c) What is the period of the box's oscillations?
    The period is 0.21666 seconds and its correct.

    (d) What is the box's maximum velocity?
    The max velocity is 127.6 m/s and its correct.

    (e) What is the box's maximum acceleration?
    The max acceleration si 3700.4 m/s2 and its correct.

    (f) How long does it take the box to move from -2.2 m to +2.2 m?
    I dont know how to approach this one either.
     
  2. jcsd
  3. Jul 4, 2011 #2

    lewando

    User Avatar
    Gold Member

    What is "sec"?
     
  4. Jul 4, 2011 #3
    seconds?
     
  5. Jul 4, 2011 #4

    lewando

    User Avatar
    Gold Member

    What did you get for part a?
     
  6. Jul 4, 2011 #5
    I did 4.4 * cos(29*2)= 2.33164. But this is not the right answer.
     
  7. Jul 4, 2011 #6

    lewando

    User Avatar
    Gold Member

    standby, please...cockpit trouble
     
  8. Jul 4, 2011 #7
    How do you do that when there's no units for the numerator? I tried doing 4.4 * cos (2pi/29 * 2), but that didnt work. How do you convert it?
     
  9. Jul 4, 2011 #8

    lewando

    User Avatar
    Gold Member

    "29/sec" is most likely Hertz (cycles/sec). Need to convert this to rad/sec. 1 "cycle" = 2pi rad. So multiply 29 cycles/sec * 2pi rad/cycle.
     
  10. Jul 4, 2011 #9
    Alright, when I converted it, my final answer was 4.386885896 and that is not right.
     
  11. Jul 4, 2011 #10

    lewando

    User Avatar
    Gold Member

    I got 4.4 (3.999 considering SDs)
     
  12. Jul 4, 2011 #11
    Its still not right. I don't understand any other way to solve for it.
     
  13. Jul 4, 2011 #12

    lewando

    User Avatar
    Gold Member

    Is there anything special about "the box shown"? I am imagining a box attached to a device that makes it oscillate according to the described function. Does it start at x=0? EDIT: when t=0 where is the box?
     
  14. Jul 4, 2011 #13
    I attached the picture. Can you see it? Its supposed to be an attachement.
     

    Attached Files:

    • box.gif
      box.gif
      File size:
      2.3 KB
      Views:
      64
  15. Jul 4, 2011 #14

    gneill

    User Avatar

    Staff: Mentor

    You might consider that 29*t/sec yields radians. No conversion required. What's 4.4m x cos(29 x 2 radians) ?
     
  16. Jul 4, 2011 #15
    I got 2.331644763, which is also not correct.
     
  17. Jul 4, 2011 #16

    gneill

    User Avatar

    Staff: Mentor

    That would be the result for 2*29 DEGREES. Try 2*29 RADIANS. Is your calculator set to degrees mode?
     
  18. Jul 4, 2011 #17

    lewando

    User Avatar
    Gold Member

    So per equation, someone pulls the box out to the right to a 4.4m hash mark then lets go at t=0.

    If 29 is in Hz, the result should be 4.4m
    If 29 is in rad/sec, the result should be 0.52m (I dont think you checked this)

    Is your answer checker caring about SDs tightly? Maybe "2 seconds" implies 1 SD.

    Running out of secret weapons.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Oscillator Questions
  1. Oscillations question (Replies: 1)

  2. Oscillation Questions (Replies: 4)

  3. Oscillation Question (Replies: 4)

Loading...