Recent content by dangus

I have a pendulum swinging with frequency w in a frictionless environment and I apply a periodic harmonic driving force also at frequency w but out of phase with the swinging pendulum. What happens exactly? Does the driving force bring the pendulum into phase with the force and then we see the...

Correct. That was my confusion. After drawing some pictures and staring at it for a bit I see it now. The analogy of flipping the track around was actually quite helpful. Thank you

I apologize for the 10 million questions. Hopefully this will be my last. Can someone explain to me exactly how the 180° pulse used to convert a T2* -> T2 signal works. I understand the concept I think. The analogy of two cars driving at two different constant speeds is often used. If...

I was also under the impression that in the quantum view the spins are only either aligned or antialigned. I obviously don't know enough to argue it one way or the other though, but I am curious to hear what marcusi says. I will share a link though, which is one of the sources I got my...

Im having another problem with the quantum mechanics view. The classical view says that we can perform a 90° pulse, a 180° pulse a 270° pulse etc with increasingly strong or long RF pulses. But in the quantum mechanics view this doesn't seem feasible. Once the protons are all elevated into...

It would seem then that my previous description of the tipping net magnetic moment was the quantum mechanics description of the system then. Correct? Assuming my description is correct, I am having trouble rationalizing something. In the quantum mechanics view T1 relaxation occurs as the...

I have another question about MRI physics. I was going to make a new thread, but it seemed easier to just post it here since you all seem to know a lot about the topic. When the perpendicular RF pulse is applied in a MRI machine the net magnetic moment tilts from the Z axis into the X-Y...

Thanks guys. I don't know enough about how the RF is actually generated though. Is it not feasible to generate RF pulses at 28GHz?

MRI imaging uses primarily the magnetic fields of spinning hydrogen protons to generate images. I read somewhere that the magnetic fields generated by spinning electrons are stronger then those created by spinning protons. Why then are electrons not used in MRI imaging? Thanks

What determines the tilt angle of a precessing proton in a magnetic field? Is it a constant the assuming no additional magnetic forces? In an NMR a perpendicular magnetic field is applied which rotates the precessing magnetic moment into the X-Y plane. After this perpendicular magnetic...

Thank you for the quick reply. I have a couple quick follow up question: If I have a spinning top in a frictionless environment set at a tilt angle θ and I wished to apply a force to increase this tilt angle how would I do that? Instinctively I would want to apply an additional force...

Im trying to understand the physics of the precession of a spinning top. What determines the tilt angle (the angle the top is tilted off the vertical axis)?