Recent content by mathman44

Homework Statement It's been a long time since I've done DE's and now I'm stuck with a monster of this form: y'(t) = a*g'(t) + b*g(t) + c*y(t) where g(t) is a known function and a, b and c are constants. What kind of DE is this, and how can I solve for y(t) -- or better yet, what...

Whoa... thanks, that's absolutely perfect.

Hi all, I'm reading the following PDF about the DFT: http://www.analog.com/static/imported-files/tech_docs/dsp_book_Ch8.pdf Please see pages 152-153. So the inverse DFT (frequency to space, x[i] = ...) is given on page 152. Then it is claimed that the amplitudes for the space-domain...

Sorry I wasn't being very clear. What I mean is that if I want to make a function that is symmetric with respect to the y-axis AND satisfies the condition above, then it would seem I can only use an odd N of samples. For example assume 15 points lie to the left of the y-axis, then by necessity...

Of course - thanks, that certainly clears it up. So an even function must always have an odd number of discrete samples (i.e. N is odd), right?

Hi jbunniii, Yes I mean DFT. Can you explain why the final element needs to be removed? In my mind the function is even since f(x)=f(-x) if you center it on the y-axis for example.

Hi mfb, I haven't assigned x values to the points. The DCT really just considers the index of each point, (n=0,1,2...N-1) and the total number of samples (N) right? But since it's even, let's say x ranges from -14.5 to 14.5 in steps of "1". The sin/cos coefficients are listed in the second...

The DCT of an even function is comprised of just cosine coefficients, correct? I'm playing around in MATLAB and I came up with a simple even function 1.0000 0.7500 0.5000 0.2500 0 0.2500 0.5000 0.7500 1.0000 0.7500 0.5000 0.2500 0 0 0 0...

Homework Statement http://postimage.org/image/j2ccrtjp1/ Here is a scan of my work. The problem is on the scan. Just trying to derive the velocity of the target in an elastic collision, as sketched in the image... Can't seem to find the problem for the life of me.

Homework Statement Consider a photon scatter off an electron heading towards the photon. After the collision the photon is scattered at 90 degrees. Find the energy E of the scattered photon. The Attempt at a Solution Boosting into the electron frame the incoming photon energy increases from...

That's precisely the explanation I gave; but if that was all that was happening, we would expect condensation between wet air of any temperature and a 'cold glass'. So the two ingredients are 1) temperature difference and 2) humidity difference. What's the physical explanation for how the...

Hello all. Consider the case whereby one brings out a cold drink on a hot day. Why do water droplets form on the surface of the cold glass? I would think that when water molecules in the gaseous state collide with the glass surface, they transfer some energy into the glass. Therefore by the...

Ah... yes, if the events occur at one location in space in one frame, they must be separated in space in the other frame. Cheers!

Hi all. I'm having trouble getting an intuitive understanding for the following situation. Let frame A and frame B be moving with relative velocity v. It's true that a clock in frame A will be time dilated with respect to a clock in frame B, but also that a clock in frame B will be time...

Hi all. I am asking for some help with getting a physical intuition for the following situation: Consider an observer and source, at rest. The source emits sound waves of a particular frequency, 'f'. Letting the medium (air for example) between the source and the observer move with a particular...