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  1. J

    Superposition of electric fields from uniform charge density

    Homework Statement Ok, here's the problem. It deals with the superposition of electric fields from uniformly charged shapes: A uniformly charged infinite plane is located at z = 0, with a surface density of charge σ. A uniformly charged spherical shell with the same surface density is located...
  2. J

    Using Fourier analysis to find frequency-amplitude spectrum?

    The signal is from a voltage supply. I see lots of pages on the internet about this, such as this one, which shows what the magnitude spectrum looks like for a square wave with an arbitrary number of co-efficients. But how would I actually create that graph myself?
  3. J

    Pressure on a submarine window problem

    I have this fluids problem I've been working on for a while, but I can't seem to get the correct answer. The problem is: A circular window with radius 25 cm in a submarine can withstand a maximum force of 1.23E6 N. If the interior of the submarine is maintained at a pressure of 1 atm...
  4. J

    Help with fluids

    I have these two fluids problems and I can't get either one (they are related). Can anyone point me in the right direction? 1. A 3.05 kg piece of wood (SG = 0.500)) floats on water. What minimum mass of copper, hung from it by a string, will cause it to sink? 2. A 3.25 kg piece of wood (SG...
  5. J

    A simple pulley problem

    I'm working on this rather simple pulley problem, and can't quite figure it out. It doesn't even involve acceleration. Could anyone help me out? Thanks. Here's the problem: A crate is pulled up using frictionless pulleys in the manner shown in the figure. The angle is 45 degrees. The masses...