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Homework Help: Please help with the ultimate physics problem! Any help would be great!

  1. Jan 6, 2009 #1
    1. The problem statement, all variables and given/known data

    A 220kg load is lifted 21.0m vertically with an acceleration a=0.150 g by a single cable. Determine:

    a. the tension in the cable
    b. the net work done on the load
    c. the work done by the cable on the load
    d. the work done by gravity on the load
    e. the final speed of the load assuming it started from rest.

    2. Relevant equations

    Not sure I wasn't in class

    3. The attempt at a solution

    I was sick with mono for a couple of months and couldn't go to school and the teacher from home and hospital school never taught me any of this, so couls someone please please help?
  2. jcsd
  3. Jan 6, 2009 #2


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    Are you familiar with Newton's laws of motion? If you are you should be able to solve the first one. Though I - or someone else - could simply give you all the equations you might need to use, if you're unfamiliar with the concepts it would ultimately be fruitless: You could do the math but other than equations there would be no significance. Would it be possible for you to make a list of what you already know, and then any explanation necessary can be given?
  4. Jan 6, 2009 #3
    Well for the first one would you do the mass times the acceleration, because from my book i think that tension equals force correct?

    but with my home and hospital teacher we never reviewed any of the other topics so im completely lost
  5. Jan 6, 2009 #4


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    Correct, assuming you use the proper value for the acceleration.

    Well, at the very least you're familiar with Newton's Laws. I can give you a brief explanation of work and energy but you should look into a better one.

    Work: The amount of work done on an object is defined to be the product of the net force acting on an object and the distance it travelled; hence we define work as W = F(d) or Work = Force multiplied by Distance. Now suppose I exert 1000 N of force on a large block that does not move. The net work I performed on the block is 0 - the block did not move. Now, suppose the block moved 0.5 m, then I performed 500 Nm or 500 J of work on the block, where J = joules. Work is also intimately related to energy: For example, the gravitational potential energy of an object is equivalent to the amount of work necessary to lift the object to a given height. While Kinetic energy is equivalent to the amount of work necessary to accelerate an object to a given speed. Standard units for energy are joules (J) while I believe the preferred units for work are Newton metres (Nm) - though this may just be what my physics teacher preferred, I'm not certain what is actually standard.

    Again, I would recommend that you get a more in depth understanding of the concepts above.
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