1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Force and Buoyancy

  1. Apr 15, 2005 #1
    Can anyone help me out. I don't know of any equation that i can us eto solve this A force 1000N is required to raise a concrete block to the surface of a fresh wate rlake. what is the force required to lift it out of the lake. I know that i need to figure out what the weight outside of wate ris, but i don't know how. no i don't know the volume the 1000N is the only info given. density is 2320 kg/m3.
    Last edited: Apr 15, 2005
  2. jcsd
  3. Apr 15, 2005 #2


    User Avatar
    Science Advisor

    If you draw a free body diagram of the block under water you should have three forces acting on it: The block's weight, the buoyancy force and the 1000N applied force. This should tell you that the force required to lift the block in air will equal the buoyant force + 1000N.

    Do you know the volume of the block?
  4. Apr 15, 2005 #3

    Doc Al

    User Avatar

    Staff: Mentor

    But are you given the density of concrete?
  5. Apr 16, 2005 #4
    The Force you need to raise the block with the volume [tex]V[/tex] to the surface is
    the force to raise the block futher is


    Then [tex]\frac{F_2}{F_1}=[/tex]
    Last edited: Apr 16, 2005
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Force Buoyancy Date
Is the buoyant force proportional to the mass? Jul 16, 2017
Calculating upthrust of float May 6, 2017
Buoyant Force Question Apr 16, 2017
Buoyancy force and floating Feb 23, 2017
Container of Liquid Accelerated Upward Jan 15, 2017