Recent content by J.Welder12

  1. J

    Escape Velocity of the Milky Way

    Homework Statement In the Solar neighborhood, the Milky Way has a flat rotation curve, with V(r)= Vc where Vc is a constant, implying a mass desnity profile ρ(r) ~ r^-2 Assume there is a cutoff radius R beyond where the mass density is zero. Prove that the velocity of escape from the...
  2. J

    Solve Obler's Paradox: Calculate Universe Size in Parsecs & Light Years

    ρHomework Statement Suppose all stars had the same radius as the Sun, and they were distributed throughout the universe with the same density as we have nearby- about 1 star per cubic parsec. Approximatly how bigh in parsecs and light years would the universe have to be in order to avoid...
  3. J

    Calculating Molecules in a punctured tire

    does m=M(molar mass)*N(number of particles) and F=pA?
  4. J

    Calculating Molecules in a punctured tire

    If a tire is punctured (or if any container full of air is holed) the air starts to leak out. Consider a small area A of the wall of the container. Show that the number of molecules striking this surface in a time interval Δt is pAΔt/2m<Vx> p is the pressure m is the average mass of the...
  5. J

    Entropy and Maximum work for two idential, finite sized bodies

    Two idential, finite sized bodies of constant volume and constant heat capacity are used to drive a heat engine- heat is taken from the hot (Th) body, work is done, and heat is ejected to the cold (Tc) body. Both bodies wind up at Tf (a) What is the change in the entropy of the system? (b)...
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