Recent content by lorenz0

  1. L

    Two ropes pulling on a cylinder that is translating and rotating on a plane

    I have solved the problem, but I am not sure if my solution is correct, so I would appreciate if someone would double check it. Thanks (a) Using an inertial reference frame in which the ##x## axis points to the left and the ##y## axis points downwards and computing the torques with respect to...
  2. L

    Optical path difference between two reflected rays

    @kuruman Got it. Thank you very much
  3. L

    Optical path difference between two reflected rays

    That was my initial guess (that the phase shifts cancel out), and in that case it seems to me that ##\Delta=\frac{2n_{soap}d}{lambda_{soap}} lambda_{soap}=\frac{2 n^2_{soap}d}{lambda_0} lambda_{soap}##, so it still is not in agreement with the stated solution
  4. L

    Optical path difference between two reflected rays

    The ray that is reflected at the air-soap interface has an optical path length of ##lambda_{soap}/2##, while the one refracted in the soap has an optical path length of ##2 n_{soap} d+\frac{lambda_{glass}}{2}## due to its traversing the soap film and also reflecting on the soap-glass interface...
  5. L

    Elliptical motion in polar coordinates

    Corrected. Thanks again.
  6. L

    Elliptical motion in polar coordinates

    I think I have completed the exercise but since I have seldom used polar coordinates I would be grateful if someone would check out my work and tell me if I have done everything correctly. Thanks. My solution follows. Since ##\left(\frac{x}{a}\right)^2+\left(\frac{y}{b}\right)^2=1## it follows...
  7. L

    Maximum voltage in the primary circuit of a transformer

    Ah, I think I have understood now. Since ##V(t)=V_0\sin(\omega t)## it must be that ##B(t)=B_0\cos(\omega t)## with ##\omega=2\pi f=\frac{2\pi}{T}=\frac{2\pi}{2\delta t}=100\pi\ \frac{rad}{s}## so that ##V(t)=V_0\sin(\omega t)=-N\frac{d\phi(\vec{B})}{dt}=-N\frac{d}{dt}\left( B_0\cos(\omega t)S...
  8. L

    Maximum voltage in the primary circuit of a transformer

    The alternating current will create an induced voltage given by ##V=-N\frac{d\phi(\vec{B})}{dt}=-N\frac{\Delta\phi(\vec{B})}{\Delta t}=N\frac{2 B_0 S}{\Delta t}=\frac{240\cdot 2\cdot 65\cdot 10^{-3}\cdot 10\cdot 10^{-4}}{10\cdot 10^{-3}}=3.12 V## and since this is the effective voltage, the...
  9. L

    Two charged spheres hitting each other

    ah, of course! I don't know how I didn't see that before, I was thinking I hadn't understood the situation correctly but it was just a typo, many thanks.
  10. L

    Two charged spheres hitting each other

    Thanks for your interest in my question. I had already included my work, the only thing left to do was to show the formula I had derived with the numbers plugged in, which I have now done. The number under the square root is actually positive, according to my calculator.
  11. L

    Two charged spheres hitting each other

    Since the forces involved (gravity and electric force) are conservative we can use conservation of energy. The initial energy is ##E_i= k\frac{q_1q_2}{r_0}-G\frac{m^2}{r_0} ## and the final ##E_f=mv^2+k\frac{q_1q_2}{2r}-G\frac{m^2}{2r} ## so from ##E_i=E_f ## we get...
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