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    Simple Machines 2: 1 Pulley Systems

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    anoeta
    SM2

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    Simple Machines 2: 1 Pulley Systems

    Uploaded by

    anoeta
    51 views1 page
    SM2

    Original Title

    SVRphy20

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    SM2

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    51 views1 page

    Simple Machines 2: 1 Pulley Systems

    Uploaded by

    anoeta
    SM2

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 1

    *01 Forces&Energy (8-45).

    qxd 25/1/07 5:12 pm Page 20

    Simple machines 2
    Key words
    1 Pulley systems
    efficiency
    force
    gear wheel
    pulley
    work

    1 Pulley systems
    ●A simple pulley does not magnify the
    force applied but changes the
    direction that the force acts. Distance force effort
    applied
    ratio is 1. to load effort effort force
    ● In 2- and 4-pulley systems a small force applied applied
    effort raises a large load. In a 2-pulley to load to load
    Simple pulley 2-pulley system 4-pulley system
    system for every 1 m by which the
    load is raised the effort is applied for 2
    m, thus the distance ratio is 2. In a 2 Screw threads
    4-pulley system the distance ratio is 4.
    ● If pulley systems were perfect
    machines they would be frictionless
    and no energy would be lost thus,
    using a 4-pulley system, a 40 N load
    would be raised 1 m by an effort of
    10 N moving a distance of 4 m. screw
    pitch water trapped by screw thread
    ● The efficiency of a machine is the ratio
    Screw-thread with a screw Raising water with a screw
    of useful work done, or energy
    output, to the work or energy input.
    efficiency = work input x 100% 3 Water wheels rotates in
    work output opposite
    direction to
    or water flow
    efficiency = force ratio x 100% rotates in same
    distance ratio direction as
    water flow
    ● The efficiency of a machine is always
    less than 100% as not all of the energy
    input does useful work.

    2 Screw threads
    ● Ina screw thread machine, the thread
    is usually turned by a handle. Distance
    ratio equals ratio of the circumference
    of the circle made by the effort to the
    pitch of the screw.

    overshot water wheel undershot water wheel


    3 Water wheels
    ● Water wheels are driven by flowing
    water.
    4 Gear wheels
    4 Gear wheels
    © Diagram Visual Information Ltd.

    ● The force ratio and distance ratio of a


    machine can be changed by gears.
    ● The 15 teeth gear makes two
    revolutions for each complete
    revolution of the 30 teeth gear. 15 teeth
    ● If the effort is applied to the smaller
    gear to drive the larger gear the 30 teeth
    distance ratio is 2.

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