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Grade 11 Physics Help

  1. Oct 27, 2004 #1
    I have a few questions I've been having troubles with, and I was hoping someone could help me out...
    1) A machine does 4000 J of work in accelerating a 20 kg object, intially at rest, at 3.0 m/s2 for 5.0s determine
    a) The efficiency of the machine
    b) The power output of the machine

    2)A block and tackle is used to raise a 100kg load. If the maximum applied force is 220N, how many strands of rope must support the moveable block?

    3)A wrench is used to turn a bolt of 6.0mm diameter. The centre of the bolt head is 0.2m from the applied force.
    a) what is the IMA of this machine?
    b) If the efficiency is 50%, what is the AMA of the machine?

    4) A ramp is 12m in length and has a grade of 25%
    a)If friction is neglected, what force is required to push a 120-kg box up the ramp?
    b) If the actual force required is 490 N, determine the efficiency of the ramp.

    If someone could help me it would be awesome!
    Nikki196 :wink:
  2. jcsd
  3. Oct 28, 2004 #2


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    Well I did this in 7th grade, what do you know so far about these problems? We wouldn't want to do your homework for you, would we?
  4. Oct 28, 2004 #3


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    IMA = DE/DR
    where DE equals the effort distance and DR equals the resistance distance.

    Properties of an ideal machine, which does not exist in reality:
    1. It is frictionless.
    2. Its actual mechanical advantage is equal to its ideal mechanical advantage.
    3. Its mechanical efficiency is 100%



    Power is work exerted over time.
  5. Oct 28, 2004 #4

    Doc Al

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    Staff: Mentor

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