Compound Machines

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Compound Machines
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Compound Machines is a 2013-2014 event for Division C in which students answer questions on simple and compound machines, and use a compound lever to determine an unknown mass. Students should bring their device and any other supplies for impound, a binder of notes, and any calculator.

Compound Machines can be considered the Division C equivalent of the Division B event, Simple Machines.



The event is split into 2 parts, the written test and testing the device. The written test will include questions on basic concepts, calculations, and the history of compound machines. For the device testing, the supervisors provide a known mass and an unknown mass and the students will determine the unknown mass by using and adjusting a compound lever. Points will be awarded for accuracy and speed.


Students may bring a single device, one binder of notes, calculators, and tools/supplies. Any materials in the binder must be able to be inverted and not fall out of the binder.


During impounding, all supplies must be impounded, including the device. All of these items must fit inside a box no larger than 100x100x50cm. This includes notes, tools, and the device itself. The calculator, however, does not need to be impounded.

Written Test


The Simple Machines page has in depth information on these devices if further reference is needed.

Machine: A mechanical device that improves or assists in labor using force inputted, and converts it do a different type of force or direction

Simple Machine: There are 6 Simple Machines. These are all different types of machines that change the input force to a different output. They are:

1) Lever

2) Inclined plane

3) Wedge

4) Pulley

5) Wheels and axle

6) Screw

Compound Machine: A machine made up of more than one simple machine. A compound Machine can allow more complex machines and more complex outputs and functions. For example, a scissor combines three different simple machines. 1) Lever- The handle, 2) Wheel and Axle: Pin to attach both sides, 3) Wedge- Blade

"Ideal Mechanical Advantage" The Ideal Mechanical Advantage is the mechanical advantage under ideal conditions, when no friction or air resistance is present. The Ideal Mechanical Advantage has different equations depending on the machine. The most simple and generic way to calculate it is using the distance in over the distance out.

"Actual Mechanical Advantage" The Actual Mechanical Advantage differs from the Ideal in that it is the actual work out over work in. This will always be lower then the ideal due to energy lost in friction and heat.

"Efficiency" Efficiency is the work out divided by the work in. Another common way to measure it is the Actual Mechanical Advantage divided by the Ideal Mechanical Advantage.

The Device

Construction Restrictions

The device must be made of two levers, directly connected, with a beam length of less than or equal to 50 cm. This is called a "compound lever." One of the two levers must be a first class lever and the other must be a second class lever.

Types of Machines

All concept questions will be limited to the topics of levers, inclined planes, wedges, pulleys, wheels and axles, and screws. See the Simple Machines page for more in-depth information.

Other machines that one may see include gears and Belt and pulley systems.