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Given time, distance and weight, how do I calculate work?

  1. Jan 21, 2014 #1
    1. The problem statement, all variables and given/known data

    a worker who carries blocks of cement from a flight of stairs to an apparatus that is 8 meters high. Every block weighs 1.50 x 10 to the second power Newtons and the worker carries 2 blocks every minute. How much work will he realize in 10 minutes and in 60 minutes?

    2. Relevant equations
    (i honestly don't know what else)
    maybe the weight formula W=mg

    3. The attempt at a solution

    I honestly have no clue.... >_<
  2. jcsd
  3. Jan 21, 2014 #2
    Hi fixedglare :smile:

    welcome to PF

    Can you tell what is making the worker spend energy?
  4. Jan 26, 2014 #3
    The weight of the blocks?
  5. Jan 26, 2014 #4
    How much work does it take to raise a single block weighting 150 N to a height of 8 m against gravity?
  6. Jan 26, 2014 #5


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    THINK! You don't use "W= mg" because you are not given m, the mass. You are given the weight, w, of 1500 Newtons, of each block and is to be lifted 8 m. What is the work done to lift one block? He lifts 2 blocks every minute so how many does he lift in 10 minutes? How many in 60 minutes?

    You state, above, that W= fd. That is, if you apply a force f over a distance d you do work w. Here the weight (not mass) is w and you must apply the force, wg, a vertical distance h. Here the weight of each block 1500 Newtons and the height is 8 m. So what work is required to lift one 1500 N block a distance 8 meters? (Be carful of the units.)

    Two blocks are lifted every minute. How many blocks are lifted in 10 minutes? How many are lifted in 60 minutes.
    Last edited by a moderator: Jan 26, 2014
  7. Jan 26, 2014 #6
    1200 j
  8. Jan 26, 2014 #7
    I know how to calculate the work itself by using the force (weight) & the distance with the W=Fd formula, I just dont know what to do with the time.

    W= 1200 J

    The question about time isn't how many blocks are lifted in 10 or 60 minutes, its how much work is realized that's what I dont understand.

    Would it be 1200 J * 600 seconds (10 minutes)?

    & 1200 J * 3600 seconds (1 hour ?)
  9. Jan 26, 2014 #8
    Doesn't the problem statement say 150 N?
  10. Jan 26, 2014 #9
    If he raises 2 blocks per minute, how many blocks does he raise in 10 minutes? In 60 minutes? How much work does he do all together during these time intervals?
  11. Jan 27, 2014 #10
    He raises 20 blocks in 10 minutes, and 120 blocks in 60 minutes.

    Do I multiply the amount of blocks per minute to my last result?

    20 blocks in 10 mins * 1200 J = 24000 J

    120 blocks in an hour * 1200 J = 144000 J

    YES! those were the results in my book, thank you so much<3 You're an angel.
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