Recent content by johnw188

  1. J

    Understanding Energy and Current in a Complex Circuit

    Remember that resistive elements cannot store energy, they only dissipate it. That said, there is a formula for the energy dissipated by a resistor per unit time, and I'm sure you've used it many times before (hint: power = ?) So your tools are KCL and KVL, right? More complex circuits...
  2. J

    How Does Opening a Valve Affect R-134a Quality and Heat Transfer in a Container?

    Nobody's going to just do your homework for you. Push in the right direction: problem relates to quality, so you need vapor dome tables.
  3. J

    Surface Area and Volume Relationships?

    Yes, pretty much.
  4. J

    Surface Area and Volume Relationships?

    Yea, I figured that one out. The question that I had when I started this whole thing out was "why?" My idea is that differentiating the volume of anything, given that the volume formula is calculated by integrating over spherical coordinates the "radius" of the object (meaning finding an...
  5. J

    How can I use math to calculate the distance of a trebuchet-launched projectile?

    This should probably be moved to the general physics section, as its not really a homework problem. That said, the explanation is long and unwieldy, though I did find a few links for you http://www.geocities.com/SiliconValley/Park/6461/ http://www.ripcord.ws/FATAnalysis.PDF <--- not sure...
  6. J

    Describe the universe in 15 words

    Generally considered a bad move ;)
  7. J

    Unraveling the Mystery of Clockwise and Counterclockwise

    A direction can be thought of in terms of a compass. Up is north, down is south, etc. The vector is pointing in that direction. However, what direction is the vector pointing in a counter-clockwise torque? (Yea yea, if you want to get picky you could point out that its based on the right hand...
  8. J

    Can You Solve This Exceptionally Challenging IQ Test?

    I liked the verbal one; I always found those quite easy. Got a 147 on it :)
  9. J

    How to Calculate Force of Water in Rotating Pail | Physics Problem

    Nay! Draw out your free body diagrams, that should help. Also, I notice a lot of people making this mistake. Saying F = ma is rarely true. Always remember to add your sigma \sum F = ma
  10. J

    Surface Area and Volume Relationships?

    So, I had a question for all of you, regarding the relationships between area and circumference, and surface area and volume. For the longest time I was confused as to how these two quantities were related. I saw that the derivative of the area of a circle was equal to its volume, but then...
  11. J

    How High Could an Athlete Jump on Mars Compared to Earth?

    Hmmm, it seems a pretty straightforward gravitation problem to me. What have you tried so far?
  12. J

    Integral Action: Value of Integrals w/ Denominators Raised to Powers 2 & 4

    Just solve them yourself, they're both pretty standard trig substitutions. You should always solve the integral forms from the table yourself, at least once, before you use them. They're a nice tool for saving yourself time and effort, not a crutch to avoid learning your integration techniques...
  13. J

    Can we stand on the surface of the Dead Sea?

    See, the great thing about physics is, we don't need to actually travel to the dead sea to figure this out ;) I haven't worked the calculations myself, but I believe James was giving the actual numbers for the dead sea.
  14. J

    Difference between kinetic energy and momentum?

    I was wondering; what exactly is the difference between kinetic energy and momentum? I was just thinking about this the other day, and I couldn't quite work it out. I'm not talking in definition-wise terms; I know that momentum=mv and kinetic energy=1/2 mv^2, and can see that the derivative...
  15. J

    Solving Rotational Dynamics: 4.0 Nm Torque, 4.0 kg Cylinder, 2.0 s

    I'm really not sure what you just wrote there, though I have a feeling you're missing something. If I'm correct, you have the form of the equation as \sum \tau = (m r^2) \alpha It also looks like you have your definition of torque mixed up. Torque is defined as such: \tau = R cross s. (what...
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