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Virtual Work Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology (台北) Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group : June 10, 2011 Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology (http Virtual Work June 10, 2011 1 / 24

虛 Virtual Work - cct.me.ntut.edu.twcct.me.ntut.edu.tw/.../aiahtm/statics/lecture2010-2/virtualwork.pdf · 移動做功. 虛功原理為白努力(Jean Bernoulli)在十九世紀所提

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  • Virtual Work

    Chen-Ching Ting()

    Mechanical Engineering, National Taipei University of Technology()

    Homepage: http://cct.me.ntut.edu.tw/E-mail: [email protected]

    CCT Group

    :

    June 10, 2011

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 1 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • 1 (Virtual Work)

    2 (Conservative Forces)

    3 (Potential Energy)

    4

    5

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 2 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • R.C Hibbeler, Statics, Pearson Education Inc., ,ISBN=978-986-154-861-6, Chapter 11, 2009.

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 3 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Virtual Work

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 4 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • (Virtual Work)

    (FR = 0)(MR = 0)

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 5 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 6 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • (Jean Bernoulli)(~F )(d~r)(dU) dU = ~F d~r (1)

    = Fcosdr (2)

    = Fdrcos (3)

    (r)(F)(U)

    U = F rcos (4)

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 7 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • (W)(NormalForce, N)(y)U = 0

    U = W y Ny (5)= 0 (6)

    y 6= 0N=W

    Fy = 0

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 8 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 9 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • ( ~M = ~r ~F )(dr = rd)(dU)

    dU = Fdr (7)

    = Frd (8)

    = Md (9)

    ()(M)(U)

    U = M (10)

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 10 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • B(U = 0)

    U = Ay (l) P(l/2) (11)= (Ay l Pl/2) (12)= 0 (13)

    6= 0Ay = P/2

    MB = 0

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 11 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 12 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • (Free-Body Diagram)(r)()(U = 0)

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 13 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Engineering Mechanics: Statics, Twelfth EditionRussell C. Hibbeler

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 13 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Engineering Mechanics: Statics, Twelfth EditionRussell C. Hibbeler

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 13 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Engineering Mechanics: Statics, Twelfth EditionRussell C. Hibbeler

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 13 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Engineering Mechanics: Statics, Twelfth EditionRussell C. Hibbeler

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 13 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Engineering Mechanics: Statics, Twelfth EditionRussell C. Hibbeler

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 13 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Engineering Mechanics: Statics, Twelfth EditionRussell C. Hibbeler

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 13 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Engineering Mechanics: Statics, Twelfth EditionRussell C. Hibbeler

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 13 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Engineering Mechanics: Statics, Twelfth EditionRussell C. Hibbeler

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 13 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Conservative Forces

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 14 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • (Conservative Forces)

    (Initial)(Final)(Path)(ConservativeForces)(W )(Fs)

    dU = ~W d~r = W (drcos) = Wdy

    U = h0

    Wdy = Wh

    dU = ~Fs d~s = Fsds = ksds

    U = s2s1

    ksds = (12ks22

    1

    2ks21 )

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 15 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Potential Energy

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 16 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • (Vg )(Ve)

    Vg = Wy (14)

    Ve =1

    2ks2 (15)

    ysys

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 17 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • (Single Degree of Freedom)(V )

    V = Vg + Ve (16)

    = Wy + 12ky2 (17)

    V12 = V (q1) V (q2) (18)

    = W (y1 y2) +1

    2k(y21 y22 )

    q1q2V (q1)V (q2)

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 18 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • (Potential Energy Criterion for Equilibrium)

    (dU)(q)(q+dq)

    dU = V (q) V (q + dq) (19)dU = dV (20)

    U = V = 0 (21)

    V = (dV

    dq)q = 0 (22)

    q 6= 0dV

    dq= 0 (23)

    dV

    dy= W + ky = 0 (24)

    yeq =W

    k(25)

    yeq

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 19 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 20 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • (One-Degree-of-FreedomSystem)Vq

    1 (Stable Equilibrium)

    dV

    dq= 0,

    d2V

    dq2> 0 (26)

    2 (Unstable Equilibrium)

    dV

    dq= 0,

    d2V

    dq2< 0 (27)

    3 (Neutral Equilibrium)

    dV

    dq=

    d2V

    dq2=

    d3V

    dq3= . . . = 0 (28)

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 21 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 22 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Engineering Mechanics: Statics, Twelfth EditionRussell C. Hibbeler

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 22 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Engineering Mechanics: Statics, Twelfth EditionRussell C. Hibbeler

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 22 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Engineering Mechanics: Statics, Twelfth EditionRussell C. Hibbeler

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 22 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Engineering Mechanics: Statics, Twelfth EditionRussell C. Hibbeler

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 22 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Engineering Mechanics: Statics, Twelfth EditionRussell C. Hibbeler

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 22 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Engineering Mechanics: Statics, Twelfth EditionRussell C. Hibbeler

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 22 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 23 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

  • (~F )(d~r)

    Chen-Ching Ting () Mechanical Engineering, National Taipei University of Technology () Homepage: http://cct.me.ntut.edu.tw/ E-mail: [email protected] CCT Group[2mm] : ()Virtual Work June 10, 2011 24 / 24

    flip_clock_black_12.swfMedia File (application/x-shockwave-flash)

    (Virtual Work)

    (Conservative Forces)(Potential Energy)