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Basic Question about Centripetal Force

  1. Sep 29, 2004 #1
    Hi. I've been having some difficulty with calculating this equation, mainly because I've forgotten most of the equations over the years, and this is sort of a reverse algebra form of an equation I scarcely remember. (i.e., I'm screwed)

    Ok, here goes.

    Assume you have objects, as per satelites(sp?) around a central field. (wewill call this central field a "planet"

    This planet has a radius of aproximately less than 25pm, or to say, 25 picometers. Some prefer this planet have a radius of 24.2 picometers, but who really cares, right ?

    The satelites or "moons" passing by this planet have an inertial velocity of
    1.8504e10 meters per second. (for the moment, we are just going to have to suspend that whole "C" thing to work out the math)

    So the question is, what would the gravitational acceleration, have to be, in order to "catch" these moons in an orbit of 25pm. Obviously we don't want much more or less than this number.

    Buddha says " If planet's gravity is too tight, moon collide with planet; but if planet's gravity is too loose, moon will fly away"

    one of the things that bugged me about this was that when gravity accelerates, you normally only count the first 50% of distance travelled, but count 100% of the speed from acceleration.

    if its easier on you, you can use picometers and picoseconds, I started to, before it got too confusing.

    As far as mass- well, a bowling ball and a feather both fall the same in vacuum, so it doesn't matter what the mass of the "moons" are. All I am ask for the aceleration rate in meters, or picometers, or kilometers, or whatever, at 25 picometers radius, each second.
  2. jcsd
  3. Sep 29, 2004 #2
    well, assuming it maintains its velocity, you can just say that a=v^2 /r where r is the orbit length plus the planets radius: 50pm, and v is 1.804e10 m/s. i think that makes sense.
  4. Sep 29, 2004 #3
    ahh, there I am :smile: I wondered where I got moved to. I think this is an ok move, and I will happily punch in the data of pperkins.

    I put it in Quantum physics originally, because its an excerpt from that area, although the question itself is pretty basic *whoo*

    I was attempting to calculate how much actual force/kinetic energy/etc. was really in an electron, assuming a cymatic oscillation of @1.2e20 hz and a 2.42e-11 m radius. Something caught my eye about an old theory postulated concerning the actual Spin of an electron, and its superluminal paradox. As a side note, some how, when punched in the numbers I came up with for its mass (based upon sqrt Gravitational constant, etc.) was virtually identical to the frequency, which was really weird.

    For one, you wouldn't think that you could get within decimal points of the scientific notion of 100 quintillion hertz, and you would probably be equally suprised if the calculator was telling you, that THAT new number, was also the "mass" in what you can only conclude is kilograms.

    I thought this was odd, but there must have been something done right, since I did not use the 6.67300 × 10-11 in my original numbers, yet it still produced a value identical... i.e., the equation was saying

    "frequency = mass"

    But that's besides the point. Just thought I would explain why my brain told me to put this part of the bigger equation in the quantum physics instead of general area.

    Thank you thank you pperkins, and anyone else who has a fun and simple way of answering the question. :D
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