Recent content by James_Frogan

  1. J

    The origins of recessive genes

    Thanks atyy, Ygggdrasil and bobze. I omitted the mutation that occurs to adapt to environments and the various other factors mentioned. About the Hardy-Weinberg problem, doesn't the recessive trait population q^2 require a large enough sample size? For the first person that received a...
  2. J

    The origins of recessive genes

    Hi everyone, I'm studying physics and not biological sciences, but I've been wondering about recessive genes recently. Given my background, do be kind on the explanations. My question is: if a recessive gene tends to be overcome by the dominant gene, how do recessive traits still display...
  3. J

    Dynamic forces acting on a rolling wheel/sphere

    Thanks Spinnor, I am aware of rolling resistance, but I believe that angular velocity of the wheel is a function of only the power required to overcome rolling resistance; whereas I am looking for a force (not power) that has velocity as a dependent. More specifically I am looking for a...
  4. J

    Dynamic forces acting on a rolling wheel/sphere

    Good afternoon, I've tried to find a simplified model for the dynamic forces acting on a rolling wheel, but have had very limited success. I'm looking for a force that is proportional (or related to) the rotational velocity of the wheel (rotational damping) because of the contact point of the...
  5. J

    Eliminating the Euler Angle singularity without quaternions?

    Thanks Mbert, I came across several articles on how to convert the angles themselves to quaternion, however the equations of motion are in the forms of: \ddot{\phi},\ddot{\psi},\ddot{\vartheta} = f(\phi,\psi,\vartheta,\dot{\phi},\dot{\psi},\dot{\\theta}), so I cannot apply the conversions in...
  6. J

    Eliminating the Euler Angle singularity without quaternions?

    Thanks Mbert, unfortunately the case I am looking at causes the top to rise to the steady position.. which unfortunately is the theta 0 position. Looks like I'll have to dwelve into quaternions. Is it possible to 'convert' my equations in Euler angles into quaternions if I have the equations...
  7. J

    Eliminating the Euler Angle singularity without quaternions?

    Hi all, I've formulated using Lagrangian formalism the equations of motion for a spinning top. I know about the gimbal lock/singularity that occurs at theta=0 and I was wondering if there was any other way to do it without dwelving into quaternions. Yogi published a paper "A Motion of Top...
  8. J

    Equations for sliding/rolling symmetric top

    Homework Statement I am attempting to derive the equations of motion for a sliding/rolling (either case or both cases) symmetric spinning top that rises under the influence of sliding/rolling friction. This is a 6 degree of freedom system with the 3 Euler angles and 3 xyz directions (although...
  9. J

    Why doesn't a spinning top fall over instantly?

    Thanks for the explanation. I merely assumed that "the angular velocity about the body z axis" was just the top's spin rate. Why does it stay as a constant of motion, but not \\omega_1 and \\omega_2?
  10. J

    Why doesn't a spinning top fall over instantly?

    I refer to the derived motions of equations here: http://www.maths.surrey.ac.uk/explore/michaelspages/Spin.htm Don't the derivations show that the rotation'' (ie psi'') is not equal to zero? Or am I confused with something else?
  11. J

    Why doesn't a spinning top fall over instantly?

    D H, if you take into account the nutation, the spin rate will not be constant but will have a slight sinusoidal increase/decrease in speed as the kinetic energy is passed between nutation and precessing. If however the case were constant precession (no nutation) then the spin rate would be...
  12. J

    Why doesn't a spinning top fall over instantly?

    I'm particularly interested in the motion of tops, from what I understand, I would have to go with Cleonis on the perpetual motion of the top. Assuming that there is no external torque or work done (i.e. the Lagrangian equations of motion simply consists of the derivatives of the kinetic and...
  13. J

    Spinning friction for a small point

    ψε∫ thank you! hahaha :P no really, you've been a great help :D thanks!
  14. J

    Spinning friction for a small point

    tiny-tim, oh dear. Physics is so mean to me :ρ now τorque comes in. Haha. Isn't torque irrelevant if it's spinning on a tip? (or perhaps just close to zero)
  15. J

    Spinning friction for a small point

    Hi cupid.callin, My guess (from what I've been reading) is that because in the theoretical we assume that the contact is perfectly flat. However in reality, for an object with a larger surface area, there will be more microscopic pimples/dimples/ridges that lock together with the contact...
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