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Homework Help: Energy Work and Power

  1. Nov 8, 2005 #1
    1. Find the power required to raise water 3m vertically from a tank and discharge it through a nozzle of cross-sectional area 0.0003m^2 at a speed of 10m/s.
    2. A mass of 1kg rests on a horizontal table. It is connected by a taut, light, inextensible string passing over a smooth fixed pulley, at the edge of the table, to another mass of 3kg hanging vertically. The 3kg mass it at a height of 0.5 metres above an inelastic floor when the system is released from rest. There is also a frictional resistance to the motion from the table of 0.5 N. Determine the total work done by the frictional force, assuming that the 1kg mass stop before reaching the pulley.
    Your help would be greatly appreciated.
  2. jcsd
  3. Nov 8, 2005 #2
    I forgot to say, these are the answers:

    1. 238.2 W
    2. 3.8625 J

    I've just no idea how to get them :-(
  4. Nov 8, 2005 #3
    well im in my first year of physics... but what is the equation of power... and then break down work into its equation..... this is just a hing to get it started... if im worng im sorry just trying to help ;-)
  5. Nov 8, 2005 #4
    KE = [tex]1/2mv^2[/tex]
    PE = mgh
    Work done = change in energy = force x displacement
    Power = rate of doing work = force x velocity
    F = ma
    It has something to do with the above formulae, but no matter how i use them I cant get the right answer.
    Last edited: Nov 8, 2005
  6. Nov 9, 2005 #5
    Please help me.
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