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Homework Help: A 1.2 kg block is pushed under water and held there. What is the buoyant force?

  1. Oct 9, 2012 #1
    A 1.2 kg block is pushed beneath the water and held there. What is the buoyant force
    (in N) acting on the block?
    (a) not enough information to answer
    (b) 11.76
    (c) 1.2
    (d) 14.56
    (e) none of these

    Since buoyant force is equal to the wt of the water displaced, I used the equation w=mg
    w=1.2 x (9.8)
    so I got 11.76 as my answer.
    Is this right?
  2. jcsd
  3. Oct 9, 2012 #2


    User Avatar
    Science Advisor

    If the bouyant force were equal to the weight, mg, it would not be necessary to push the block under water- it would float at whatever depth you placed it. The bouyant force is equal to weight of water displaced. The bouyant force is, as you say, the weight of the water displaced- and that will be equal to the density of water times the volume of the block.
  4. Oct 9, 2012 #3
    Thank you!!!! It makes sense now
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