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!

Homework Help: Problems of statics, angular motion and simple harmonic motion

  1. Jan 6, 2013 #1
    All Questions are shown on pictures.

    My Calculated answers:

    A1(a) R= 19.21∠68.7o N
    (b) E = 19.21∠-111.34o N or = -19.21∠68.7o N <--- Is't either one answer is correct or not? If not, which answer is correct and why? Thanks.

    A2(b) I = 0.5mr2 = 1.125kgm2
    A2(a) k=(I/m)1/2 = 0.212m
    A2(c) αt=ω, α = 3.14 rad/s2
    A2(d) T=Iα = 3.53Nm

    I can't gain the answer of A2(a) first. I use the A2(b) answer to help me to gain the A2(a) answer. So, the step of my calculated order is A2(b) -> A2(a) -> A2(c) -> A2(d). Is't correct?

    B1(a)(ii) RBY = 1500N

    sum of force and moment = 0

    RA = 1200N (toward left)
    RBX = 1200N (toward right)

    B1(b) RBY = 500N
    RA = 2012.4N (toward left)
    RBX = 1146.4N (toward right)

    B2(a) KE = (0.5)(10)(100) = 500J
    (b) PE = (10)(9.81)(147.8) = 14503.1J
    (c) v2 = {[(500 + 14503.1)x2]/10}0.5 =54.8m/s
    (d ) WD = 1.2(230) = 276J , v= {[(15003.1-276)x2]/10}0.5 = 54.3m/s

    B3(a) n = 1/0.08 = 12.5Hz
    (b) m = (0.08/2π)2(20x103) = 3.24kg
    (c) ω = 2π(12.5) = 78.5rad/s, v=78.54x0.01 = 0.785m/s
    (d) f = 78.542(0.006) = 37.01m/s2 , T = 2π(0.006/37.01)0.5 = 0.08s
    (e) I can't do this part, may you help me, please?

    All Questions are shown on pictures.
    All above my calculated ans. are correct or not? It there are something wrong, please don't hesitate to correct my answers and give some comment. Thanks a lot.

    Attached Files:

    • A1.JPG
      File size:
      14 KB
    • A2.JPG
      File size:
      31.8 KB
    • B1.jpg
      File size:
      18.4 KB
  2. jcsd
  3. Jan 6, 2013 #2
    Questions of pictures B2 and B3

    Attached Files:

    • B2.JPG
      File size:
      50.2 KB
    • B3.JPG
      File size:
      45.3 KB
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook