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What’s up with momentum?

Published on 28 Comments on What’s up with momentum?

Why is there no name for a unit of momentum? Or for angular momentum? Did we run out of famous people to name things after?

How about one sina or one descartes for linear momentum and one foucault for angular momentum?

UPDATE: More here.

28 thoughts on “What’s up with momentum?”

      2. stilesroasters

        The other property that needs better naming is the opposite of dense. When something has high density we say it is dense. When it has low density we say it is not dense, which does not convey that it might be lower density than average.

        Bugs me.

    2. AnnieDunkin

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  2. Coby Beck

    Because motion is a relative property? Momentum is really just inertia (mass) times velocity, and velocity is relative to some frame of reference. (not an expert opinion, just thinking out load)

  3. Salamander

    Don't go proliferating units unnecessarily. If something can be simply described in terms of (let's call them) basic units, do it.

  6. different_name

    This is evidence of either Kevin indulging in weed, or perhaps a long, late-night phone call with a college friend.

  7. reino2

    Don't assume that there is only a metric unit. There could also be imperial units. 36 donks=12 skrings=6 smofs=1 blov.

  8. J. Frank Parnell

    In the special theory of relativity, momentum and kinetic energy are combined into a four vector. Kinetic energy (usually expressed as kinetic energy divided by the speed of light) can be thought of as the time component of momentum, which together with the three spatial components of momentum forms the four vector.

    3. ScentOfViolets

      Right! And since most of the regulars here can cog on to it if they don't know it, the four-moment is associated with the equaiton E^2=(p c)^2+(m_0 c^2)^2. Yikes,that looks nasty!

  9. ssittig1

    Speaking of units needing naming or renaming, I nominate the Astronomical Unit.

    The AU is a really dumb name -- like calling the mile an 'Earth Unit.'

    1. Salamander

      Good idea! How about calling it
      * the Kepler? Because he realized the Earth went around the Sun, and not vice versa
      * the Solar Yardstick: because, in the solar system, it's still all about us

      2. Solar

        Mach isn't actually a unit of speed per se. It is a ratio of flow velocity within a boundary relative to the speed of sound.

  11. Conjoman

    We do have a unit for angular momentum, it's called "spin".
    Momentum is sometimes referred to as "impulse" so perhaps the unit could be "pulse".

    1. reino2

      Spin is not a unit. At the subatomic level, spin is often given in units of reduced Planck constants, which is based on Joules * seconds.

  12. kaleberg

    As lawnorder noted, we don't have units for speed. We tend to have units for things we can measure more or less directly like pressure, temperature, force, length, time and mass. If we have to measure several things, we tend to not to bother creating a special unit.

    My favorite question about units is: why do we see capacitors rated in picofarads and microfarads, but never in nanofarads? There was IEEE discussion on this with inconclusive results.

    Then there are the cosmologists who measure distance, time and mass in meters so that velocities are dimensionless. Worse, their periodic table goes hydrogen, helium, metals.

  13. Pingback: Emmy Noether and the conservation of momentum – Kevin Drum

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