Recent content by mic*

  1. M

    Can Snails Swim? Mystery at the Museum

    How does one become expert enough in snails to identify this particular one as a land species, yet be unfamiliar enough with their behaviour to pose such a question?
  2. M

    Automotive Death of a car battery and related issues

    @CWatters, I just had a bit of a dig around and I must admit it is hard to find proprietary info on SC use in fuelled vehicles, especially without being used in connection to some form of kinetic energy recovery system. Ie, an SC integrated ONLY for stop-start battery support.
  3. M

    Automotive Death of a car battery and related issues

    Larger bttery units seem to be another approach. SC's are rated at >500,000 cycles so they are not considered a servicable part. They will outlast your steering wheel.
  4. M

    Automotive Death of a car battery and related issues

    In short, no. Maybe in the past it could not have worked so well, but electronic fuelling and engine sensing is relatively precise these days. The engine will be warm, so there will be no "cold start" enrichment. And the engine knows exactly where it is so you generally find they fire...
  5. M

    Automotive Death of a car battery and related issues

    New generation stop-start features are engineered somewhat differently to older lead-acid systems. For example, they may contain a supercapacitor (very low impedance = very fast charging) to support a sealed gel-electrolye battery. Although 30min minimum charge for one start is very...
  6. M

    Gas adsorption for (BET) surface area of graphene oxide based thin films

    TGA suggests it will be fine so I am actually doing that already :) I expect it to be a high SSA material - the rGO. Unless all the graphene sheets have restacked, which is possible but not probable. But I see ypur point. I might run the same size sample of graphite as a comparison. Cheers
  7. M

    Gas adsorption for (BET) surface area of graphene oxide based thin films

    Thanks for the advice mjc123. I am pretty sure I have no leaks. I ran an activated carbon sample for comparison and it produced a lovely microporous isotherm. There is something going on with the sample. I thought perhaps it was thermally related. The sample itself consists of little chopped up...
  8. M

    Gas adsorption for (BET) surface area of graphene oxide based thin films

    I am using a Micromeretics ASAP2020 machine. The sample is ~25mg of reduced graphene oxide based film. The problem is I am getting adsorption isotherms showing negative volumes of adsorbate (N2) entering the tube as P/P0 increases. The sample was degassed prior to testing at 250°C for 3...
  9. M

    Conundrum about meaning of "Dwell" and "Dwell Meter"

    I've only ever used a dwell meter that was a function on a digital multimeter. The number of cylinders was a selectable setting, like resistance range might be. I always imagined it would have a PLC in it that was measuring duty cycle and running a simple internal calculation...
  10. M

    Conundrum about meaning of "Dwell" and "Dwell Meter"

    This is far less reliable when you consider how the components can wear.
  11. M

    A question regarding the Centripetal force

    Hi Ashton, you just said there is no friction. So is the ball rolling, or is it sliding? Generally in this kind of problem 'no friction' would imply no rolling friction, meaning no deformation of the surfaces, and no torque imparted by the normal force.
  12. M

    A question regarding the Centripetal force

    It helps to establish a coordinate system. While you are on the right track with your formula and your diagram, I feel there are essential bits missing from the diagram, and errors in the formula. There is a *possible* coordinate system drawn below and some relations that might help you to see...
  13. M

    A question regarding the Centripetal force

    Consider when X = 90°. Your equation breaks down because the LHS will be zero but yet there should an 'mg' term still acting. Only the normal force from the hemisphere will have gone to zero. The total forces acting on the ball at any time are Ftot = Fg + Fn + Ff Where Ff is the frictional...
  14. M

    Why are astronauts outside a spaceship not pulled by Earth's gravity?

    I did not equate stable with circular. I provided the formula for a stable circular orbit without explicitly stating that it was a simplification only applicable to circular orbits.
  15. M

    Why are astronauts outside a spaceship not pulled by Earth's gravity?

    Thankyou for pointing out the quote feature. Should I have used it now, or will chronological progression of posts suffice? Without tangential velocity there is no centripetal acceleration, just straight line acceleration due to gravitational attraction. The vector for this acceleration is not...
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