Time derivative Definition and 60 Threads

  1. X

    Time derivative with three variables

    Homework Statement Im am attempting to solve very difficult kinematics for a problem in my Dynamics course, and after what I got for the velocity of the particle, I come accros the problem that i can't diferentiate one part. Essentially I have to get the time derivative of...
  2. B

    Derivation of the ordinary time derivative of the energy associated with a wave

    Okay, so I'm at a loss for words to describe my irritation and curiosity on how this is solved. Given the one-dimensional wave equation (i.e. u_tt=c^2*u_xx 0<x<L, t>0) with no source and constant velocity, we define the energy associated with the wave to be E=integral from 0 to L of...
  3. J

    Third order time derivative of displacement

    Hi i was just wondering why do we stop with only the second order derivative of displacement which is the acceleration. I was wondering if there is no scenario in the world where we would need the third order time derivative which might talk about how the acceleration varies with respect to...
  4. D

    Time derivative of relativistic momentum help

    How does one take the time derivative of ϒmv ? I tried treating gamma and mv as separate functions but it just gets messy and ultimately wrong.
  5. Peeter

    Lagrangian question. ability to remove time derivative terms.

    In the solution of a pendulum attached to a wheel problem, I was initially suprised to see that a term of the form: \frac{df}{dt} "can be removed from the Lagrangian since it will have no effect on the equations of motion". ie: L' = L \pm df/dt gives identical results. f in this...
  6. L

    Hermitian adjoint of the time derivative?

    So I had a QM test today and I needed to show that the energy operator is hermitian. This was easy to show provided that the the adjoint of d/dt is -d/dt. I know this is the case for the spatial derivative but is it the case with the time derivative? The bra-ket is an integral over x not time...
  7. Y

    In-frame time derivative proof

    Could someone please help with this question. For non-inertial frames show that the in-frame time derivative D obeys: D(fa)=fDa+df/dta Where f is a scalar function and a is a vector. I know that Df=df/dt and that Da= the sum of the derivatives of the components of a times the relavant...
  8. G

    Quantum: Finding time derivative of momentum operator in terms of V(x)

    Hi all, got a little caught up in tonights homework assignment; which basically reads: Find an expression for \frac {d<\hat{p}>} {dt} in terms of V(x). I had a few ideas from my math methods for theoretical phys. class i took a few quarters ago, involving applying the derivative operator...
  9. E

    Engineering Connecting RL Combination to Output Time Derivative of Input Voltage

    1-How could an RL combination be connected to produce an output voltage which is the time derivative of the input voltage? 2-Show that taking the time derivative of a sinusoidal function [such as cos(wt+a)] always has the effecton increasing its phase pi/2. 3-İf the internal series...
  10. Loren Booda

    Force=mass times acceleration, or time derivative of momentum?

    Which is more generally corrrect, F=ma or F=dp/dt ?
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