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Diamond tip presses physics

  1. Feb 25, 2008 #1
    1. The problem statement, all variables and given/known data
    Diamond tip presses are now capable of creating pressures in excess of one million atmospheres. Suppose the tips of the presses were circles with an diameter of one millimeter. How much force must be applied to the tips to create a pressure of one million atmospheres?

    2. Relevant equations
    P = F/A, where P is the pressure, F is the force and A is the area.
    r is the radius in my solution.

    3. The attempt at a solution
    P = 10^6 atm, r = 1.97 x 10^-2 in
    P = (10^6)(14.7 lb/in^2) = 1.47 x 10^7 lb/in^2 (unit conversion)
    A = (pi)(1.97 x 10^(-2))^2 = 1.22 x 10^(-3) in^2

    F = PA = (1.47 x 10^7 lb/in^2)(1.22 x 10^(-3) in^2) = 1.79 x 10^4 lb
    Did I do anything wrong? I just want to make sure.

  2. jcsd
  3. Feb 25, 2008 #2


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    Looks good. But you might want to convert the force to Newtons since the diameter was given in millimeters (personally, I like it in pounds).
  4. Feb 25, 2008 #3
    So, it doesn't really matter if pounds is used or Newtons is used?
  5. Feb 26, 2008 #4


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    The USA, Myanmar, and Liberia use pounds as the standard unit of force. Everywhere else in the world, the Newton (SI system) is the standard unit of force. Since the problem noted the diameter in mm, it may be looking for Newtons of force, not pounds, because it's bad enough working with 2 systems, let alone mixing the two. Being from the States, I like pounds, because I get a good 'feel' for how much 18000 pounds is. When you convert pounds to newtons, 18000 pounds is about 80000 newtons. I wouldn't have a good feel for how much 80000N is without first converting it to pounds. If this is a Physics problem where you are asked to use SI, use Newtons.
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