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INPUT   DATA

♥ EXAMPLE Of Input/Output

Title

Radius of larger pulley, R		cm
Radius of smaller pulley, r		cm
Weight to be lifted, FW		N
Lifting force, FL		N

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OUTPUT   VARIABLES   &   GRAPHS

Variables	Values	Units
♦  Ideal mechanical advantage
♦  Actual mechanical advantage
♦  Efficiency		%

Force & Acceleration

A machine is a device in which the method of application of a force is changed to achieve some advantage. Examples are: lever, pulley, crank and axle.

The actual mechanical advantage (AMA) of a machine is given as:
AMA = force ratio = [force exerted by machine on load]/force used to operate machine]

The ideal mechanical advantage (IMA) is give as:
IMA = distance ratio = [distance moved by input force]/[distance moved by load]

Efficiency = [power output]/[power input] = AMA/IMA

Consider a differential pulley (chain hoist) system comprising of two toothed pulleys fastened together and rotating on the same axle. A continuous chain passes over the system as shown in the figure. The following equations apply:

  AMA = F_W/F_L
   IMA = 2R/[R - r]

where
     R = radius of wider pulley
     r = radius of smaller pulley
     F_W = load to be lifted
     F_L = lifting force applied by the operator

Tips

    ◊ Use link EXAMPLE Of Input/Output  to demo data entry expectations and results; you may edit & use it as starting point

BIBLIOGRAPHY

• Bueche FJ & Hecht E; College Physics, Schaum's Outlines Series; McGraw Hill, New York, 1997.
• Lowe TL & Rounce JF; Calculations For A-Level Physics; Nelson Thornes Ltd, Cheltenham, UK, 2002