Recent content by enfield

ah k. i followed the link to specific impulse and it helped me understand. http://en.wikipedia.org/wiki/Specific_impulse and it says the effective exhaust velocity is also the thrust divided by the rate of the flow of mass from the rocket. that makes sense. (and yeah, this is with the...

How would the equation look if instead of knowing the effective exhaust velocity we knew the force the exhaust was exerting on the rocket. The equation is: \Delta V = v_e * ln(\dfrac{m_0}{m_1}) would \Delta V still be proportional to the log of the initial mass over the final...

\dfrac{\mathcal{F}^{-1} \Big( \sqrt{\mathcal{F}(f(x))} \Big)}{f(x)} = g(x) g(x) is known, and for an example let's say g(x) is something simple like g(x) = x so we have \mathcal{F}^{-1} \Big( \sqrt{\mathcal{F}(f(x))} \Big) = x \cdot f(x) my question is, how do i find f(x)? it's...

A is a square matrix. x, b are vectors. I know for Ax=b, that given b, there are an infinite number of pairs (A, x) which satisfy the equation. I'm wondering if the same is true for xAx=b. in particular, what if (x, A, b) are all stochastic vectors/matrices (i.e the entries of b and x add to...

if I have square matrix A whose decimal elements a_{i,j} = \frac{v_i}{v_j} how do I find (or approximate) the vector that would produce the matrix elements. what's a good way to do that? i guess you can scale the vector however you want and it'll still produce the same matrix.. thanks.

thanks for the thoughtful response! okay, i hadn't read about tensors yet when i posted this - just the definitions of contra- and co-variant vector components. now i have a bit though. As I understand them, the contra- and co-variant components of a vector can be defined in many ways (as the...

Can the covariant components of a vector, v, be thought of as v multiplied by a matrix of linearly independent vectors that span the vector space, and the contravariant components of the same vector, v, the vector v multiplied by the *inverse* of that same matrix? thinking about it like that...

Can the covariant components of a vector, v, be thought of as v multiplied by a matrix of linearly independent vectors that span the vector space, and the contravariant components of the same vector, v, the vector v multiplied by the *inverse* of that same matrix? thinking about it like that...

I thought the external magnetic field had to vary within an object in order for that object's magnetic moment to line up with the field.

thanks for the explanation! I figured out why by finally being directed here yesterday http://en.wikipedia.org/wiki/Dispersion_relation.

hmm I've been trying to understand this myself recently. TobyC's derivation is convincing to me! but I don't understand part of wikipedia's thermodynamic derivation still (specifically how the simple differential equation is obtained from equating the second derivatives of entropy). If anyone...

ah thanks so much for that link :smile:.

While gravitational redshift refers to what is seen, gravitational time dilation refers to what is deduced to be "really" happening once observational effects are taken into account. When using special relativity's relativistic Doppler relationships to calculate the change in energy and...

It's going to take me awhile to digest your answer. but thank you so much! Even if I can't extract everything from your answer I feel it's given me some direction. I think i need to soundly understand Lorentz transformations first. Yeah, if understanding how time is calculated in generalized...

I know I spelled dilated obscenely wrong in the title. I'm sorry! == Is the connection that in both time dilation due to faster movement through space, and time dilation due to movement into lower gravitational potentials, the flux of "gravitons" through the object increases? (of course that...