http://www.ck12.org Chapter 8. Work, Power, and Simple Machines
Screw
Ascrewis an inclined plane wrapped around a cylinder. When on a screw, inclined planes are called threads, which
can be seen in the image above. The mechanical advantage of a screw increases with the density of the threads. The
calculations to determine the IMA for a screw involve the circumference of the head of the screw and the thread
width. When the screw is turned completely around one time, the screw penetrates by one thread width. So, if the
circumference of the head of a screw is 3.0 cm and the thread width is 0.60 cm, then the IMA would be calculated
by
IMA=resistance distanceeffort distance = 03. 60.^0 cmcm= 5.
Whensimple machinesare joined together to makecompound machines, the ideal mechanical advantage of the
compound machine is found by multiplying the IMA’s of the simple machines.
Summary
- A machine is an object or mechanical device that receives an input amount of work and transfers the energy
to an output amount of work. - For an ideal machine, the input work and output work are always the same.
- The six common simple machines are the lever, wheel and axle, pulley, inclined plane, wedge, and screw.
- For all simple machines, the ideal mechanical advantage isresistance distanceeffort distance.
- For all simple machines, the actual mechanical advantage isresistance forceeffort force.
- When simple machines are joined together to make compound machines, the ideal mechanical advantage of
the compound machine is found by multiplying the IMA’s of the simple machines.
Practice
Use this practice quiz to check your understanding of work and simple machines.
http://www.proprofs.com/quiz-school/story.php?title=physics-chapter-10-energy-work-simple-machines