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Mechanical Engineering Dynamics Problem

  1. Nov 8, 2013 #1
    1. The problem statement, all variables and given/known data A plastic film moves over two drums. During a 4s interval the speed of the tape is increased uniformly from v0= 2ft/s to v1= 4ft/s. Knowing that the tape does not slip on the drums, determine (a) the angular acceleration of drum B, (b) the number of revolutions executed by drum B during the 4s interval.

    diagram of problemhttp://www.chegg.com/homework-help/questions-and-answers/plastic-film-moves-drums-4s-interval-speed-tape-increased-uniformly-v0-2ft-s-v1-4ft-s-know-q3878687


    2. Relevant equations[itex]v^{2}_{f}[/itex]=v[itex]^{2}_{0}[/itex]+at
    v=r[itex]\omega[/itex]
    a[itex]_{t}[/itex]=r[itex]\alpha[/itex]



    3. The attempt at a solution I used the first equation to find that the linear acceleration of the tape is 3 ft/s^2. Since it's translating to drum B I would assume that the point that it touches the top of drum B would also have a linear acceleration of 3 ft/s^2 I then used my 2nd equation to figure out the angular acceleration of B by taking its radius of 15 in or 1.25 ft and dividing it from the linear acceleration coming up with 2.4 rad/s^2 but the back of the book states .400 rad/s^2

    Where am I going wrong?
     
  2. jcsd
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