What are the fundamental methods of generating motion?

  1. I know that motion today is usually generated by


    - generating a varying magnetic field and varying it in relation to a fixed one
    - ccombusion engines

    Are there other "fundamental" approaches to generate motion, or is that pretty much it?


    Your input is appreciated, thanks!
     
  2. jcsd
  3. NascentOxygen

    Staff: Mentor

    hydraulics are behind the movement of many mechanical arms and levers, e.g., ditch diggers, elevators, car brakes, jacks
    pneumatics is good for lower-powered but faster acting arms and levers, e.g., air brakes, industrial robots
    springs power the movement in older clocks and watches and parking meters
    (wind moves sailing vessels and turns windmills)
     
    Last edited: Nov 18, 2013
  4. Bandit127

    Bandit127 205
    Gold Member

    Steam (unless you include that in combustion engines).
    Gravity.
    Muscle power.
     
  5. Ejecting mass to create a reaction force (think rockets or ablation) is another one.
     
  6. Very exciting contributions!

    Don't Hydraulics merely transfer motion? (as opposed to generate it)

    Also, imho, I.C., steam and rocket engines are fundamentally related.

    I would then categorize the main methods of generating (continuous) motion as based on:

    - Electromagnetism
    - Combusion (Steam, jet, etc.)
    - Potential (Gravity, springs, pneumatics)
    - Other external flow (wind)

    And maybe also
    - Ionization (plasma)
    - Organic (muscle)

    Further contributions and corrections are welcome.
     
  7. Baluncore

    Baluncore 2,516
    Science Advisor

    Expansion or contraction without phase change of a solid, liquid or gas.
    Solid = Bi-metalic strip.
    Liquid = Thermometer.
    Gas = Stirling engine.

    Piezoelectric transducer.
    Magnetostriction.
    Radiation pressure.
     
  8. In the most general sense, I think when you say "motion" you probably mean work. In this case, work is defined as a force acting over a distance, W=F*d. The units for this are Joules, which is the fundamental unit of energy. According to several laws of thermo. energy cannot be created or destroyed, only exchanged. So by these definitions, all motion is transferred, and none of it is "generated".
     
  9. Baluncore

    Baluncore 2,516
    Science Advisor

    IMO... “motion” means movement, not work.

    So, are you are defining the question out of existence?
    Or are you saying we live in a perpetual motion machine?

    IMO.
    An engine converts energy from one form to another.
    A mechanism is a mechanical machine that converts one motion into another.
    A motor is an engine or mechanism that produces motion.

    So is a hydraulic motor a mechanism or an engine?? It converts pressure into motion but the working fluid moves. The pressure in the fluid was originally generated by a moving pump.

    Likewise, an electric motor has a moving fluid. Power is also electron pressure times current flow.
     
  10. Right, but all motion is is the change of position w.r.t. time. Since we're talking about methods of generating motion in the engineering forum, than we have to inherently talk about forces being applied over distances.

    So if we're talking about work (or power) than we can break down the types of power sources. These power sources are the "fundamental methods of generating motion". As far as I can tell, we essentially know about every type of power source (I guess except for some futuristic quantum mechanical source).

    These things you're talking about; engines, mechanisms, motors, and I can include machines, all have well defined definitions.

    Hydraulic motors convert pressure into torque. That makes it to be defined as an actuator, and an actuator is a mechanism. A pump by this logic, is also a mechanism.

    I guess to contribute to the thread, nuclear power I think is pretty fundamental. Geothermal sources, which is just simply fluid pressure from a temperature gradient from gravity.
     
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