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Homework Help: Acceleration in a Pulley System

  1. Jan 22, 2008 #1
    Hey, I'm doing a review packet for my AP Physics class, and I was just looking for some confirmation that I'm on the right track.

    Here's the image of the problem: http://img297.imageshack.us/img297/2681/imgrx6.jpg [Broken]

    Ignore the scribbles. i'm using the formula a = ((mB)(g)- (µ)(mA)(g)(cos Ø)) / (mA + mB), and i'm pretty sure the answer is 2 m/s/s for both parts a and c.

    Can anyone confirm/deny? Thanks.
     
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Jan 23, 2008 #2
    you are missing something...

    applied force-friction=mass*accln
    50-[.2*100]= 10 *a

    >50-20=10*a
    >30=10*a
    >a=3m/s^2

    this is enough for ya to proceed in second case...

    go ahead...
     
  4. Jan 23, 2008 #3

    Doc Al

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    Staff: Mentor

    Since the situations are physically different, the acceleration will be different. Don't use a canned formula* (which applies only in special cases). Instead, learn to apply first principles (force analysis and Newton's 2nd law)--then you can solve any problem tossed at you without having to memorize dozens of limited-use results.

    *Does that equation even make sense for case I? There's only one mass.
     
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