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    heyyalliee's Avatar
    heyyalliee Posts: 37, Reputation: 1
    Junior Member
     
    #1

    Oct 4, 2010, 09:42 AM
    Ideal Pulleys
    Mechanical Advantage-
    The pulley system shown in the figure is used to lift a 52- crate. Note that one chain connects the upper pulley to the ceiling and a second chain connects the lower pulley to the crate. Assume the masses of the chains, pulleys, and ropes are negligible.

    Q1: Determine the force required to lift the crate with constant speed.

    Q2:Determine the tension in the upper chain.

    Q3: Determine the tension in lower chain.


    Okay so to find Force I did:
    Fnet=F+F-mg
    F=Mg/2

    52(9.81)/2 =255.06 or 260( they want it in 2 sig figs)
    When I checked answer it said this was not right?!

    What am I doing wrong.

    I know top and bottom tension should equal. I'm just having a hard time finding F.

    Thanks for help
    Unknown008's Avatar
    Unknown008 Posts: 8,076, Reputation: 723
    Uber Member
     
    #2

    Oct 4, 2010, 09:51 AM

    Um... there is no image :(
    heyyalliee's Avatar
    heyyalliee Posts: 37, Reputation: 1
    Junior Member
     
    #3

    Oct 4, 2010, 11:21 AM

    Here you go:



    If that doesn't work. Here is link.
    http://www.flickr.com/photos/49708296@N04/5051943688/
    ebaines's Avatar
    ebaines Posts: 12,131, Reputation: 1307
    Expert
     
    #4

    Oct 4, 2010, 12:42 PM
    Quote Originally Posted by heyyalliee View Post
    Okay so to find Force I did:
    Fnet=F+F-mg
    F=Mg/2

    52(9.81)/2 =255.06 or 260( they want it in 2 sig figs)
    When I checked answer it said this was not right?!
    Perhaps they used a value of g = 9.8 m/s^2? That would give an answer of 52(9.8)/2 = 254.8 N, which rounds down to 250 N.
    Unknown008's Avatar
    Unknown008 Posts: 8,076, Reputation: 723
    Uber Member
     
    #5

    Oct 5, 2010, 12:19 AM

    Yes, giving 52 kg (which is 2 sf) suggests that you use g = 9.8 m/s^2 (which is 2 sf) and the answer in 2 sf too.

    The next two parts should be easy :)

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