Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Tension in lifting cable

  1. Jul 1, 2007 #1
    1. The problem statement, all variables and given/known data

    A seagoing crane lifts a sealed safe from a sunken ship. The average density of the safe is 5.3 grams/cc and its mass is 120 kg. What is the tension in the lifting cable when the safe is still submerged?

    2. Relevant equations

    Pressure = density *gravity* height*
    Buoyant force = mg

    3. The attempt at a solution

    I calculated 5300kg/m^2 * 9.81 m/s^2 * 120 kg

    The above is what I got so far but I'm not sure I'm doing it right. Any help would be greatly appreciated.
     
  2. jcsd
  3. Jul 1, 2007 #2
    Draw a free-body diagram of the object. From the context of the problem, there must be no net force acting on the object. What forces act in which directions?

    Note: the buoyant force is equal to the weight of the DISPLACED fluid, not necessarily equal to the weight of the submerged object.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook