Recent content by davidchen9568

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    Quantum Harmonic Oscillator

    You are missing an x^2 in #3.
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    Variable mass system - sand falling on flatcar

    F=ma can be applied, but that will only make the problem more complex. If you apply it to (flatcar + sand on it), you need to find the forces acting on the system. Sand falling on the flatcar exerts a force to it, because friction has to act on the sand to accelerate it until its velocity equals...
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    Efficiency of a engine

    Thanks for the reply. Now the problem is solved. Diesel cycle - Wikipedia, the free encyclopedia
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    Efficiency of a engine

    Homework Statement Four thermodynamic processes A,B,C,D are shown in the picture. A and C are adiabatic processes. Pressure is held constant during B, and volume is constant during D. An engine run from A->B->C->D->... What is the efficiency of this engine (in terms of V1/V2)? Homework...
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    Integrating dx/dt=k(a-x)(b-x)

    In the original post. t=0 when x=0.
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    Magnetic Induction (Non-uniform Current)

    Because J is a function of radius. I=\int { J\cdot dA } The second method looks fine. For the second question: What is the enclosed current outside? Is it zero?
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    Integrating dx/dt=k(a-x)(b-x)

    Looks like I get x=\frac { a{ e }^{ r }-b }{ { e }^{ r }-1 } \\ r=(b-a)(kt+c)
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    Integrating dx/dt=k(a-x)(b-x)

    What are the values of a,b, and k?
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    Question about Eötvös experiment

    Thanks a lot for the link. I will read them.
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    Question about Eötvös experiment

    I do not understand the concept. Let the centrifugal forces on the two objects are F1 and F2. The rod will not rotate because net torque is 0. That is, F1r1=F2r2. That Does that mean we have to carefully adjust the positions of objects (before experiment) so that m1gr1=m2gr2? Then we conclude...
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    Help with piston and atmospheric pressure

    P1 is the initial pressure. Look at the piston. There is a upward force produced by air inside, which equals P1 times S. Two downward forces are atmospheric pressure and weight. This gives the first equation, and the second one is similar.
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    Finding max. velocity of jet w/ constant and/or changing acceleration

    In the case when mass changes (because of fuel), F=ma no longer helps. Try F=dP/dt
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    Triangle Inequality Proof

    Write down the triangle inequality. You need a minus sign, which can be obtained by moving something to the other side of the inequality.