## Simple Machines

Simple Machines

Description: Participants will identify, use, and answer questions about simple machines and recognize the relationships between work, force and distance as they apply to each simple machine. Knowledge of the following six simple machines will be demonstrated:  lever, inclined plane, pulley, screw, wheel and axle, and wedge.

Event Supervisor:
Artie and George Martin

 From the Event Coach Workshop. Sample test questions Event Coach Workshop slides Click here to watch the very informative Workshop Video This event uses a ZipGrade optical answer sheet  Click to Learn more Event Coach Workshop recap- be sure you're using the latest rules See the Elementary Workshop List for this season Report problems at This email address is being protected from spambots. You need JavaScript enabled to view it.

#### What class of lever do you consider a pizza cutter to be? We have received different answers to this question from different sources.

The pizza cutter was used as an example of a tool where the fulcrum is considered to be the wrist or elbow of the user.  Therefore, it is a third class lever.

#### On the sample test from 2014, question 40. The answer key says that the answer is C. Should the correct answer be A?

You are correct that the answer key is wrong.  The intent was to have two pulleys with the same Mechanical Advantage, but where one changes the direction of force but the other does not. However, the example was not well thought out.

The test you have from 2014 was the test used for the district competitions.  It was provided to coaches, for reference only.  It should have been destroyed after reviewing with the students in preparation for that year's regional competition.

#### How are you going to treat pi since the kids will not be able to bring in calculators?

No.  Only simple calculations are necessary and do not require the use of a calculator.  Scratch paper is provided for this purpose.

#### In the case of screws, will you be giving them the pitch?

In the case of screws, students may be asked to evaluate how a change in diameter, or pitch will change the mechanical advantage.

#### How will you be handling pi in those instances where it needs to be used?

Students will not use Pi in calculations.  They only need to know when a formula for determining mechanical advantage includes Pi.  Students will only be asked to estimate or approximate mechanical advantage.

#### Will screw drivers be deemed a lever and a wheel and axel? Or will it only be called a wheel and axel if the picture shows someone using the screw driver to put in a screw? Also, are screw drivers considered wedges? Are things like spatulas considered wed

When determining which simple machine a tool is categorized as, we use the original design of the tool.  That means that a screwdriver, a tool designed to insert screws, is a wheel and axle.  Yes many people use a screwdriver as a lever, for instance to open a paint can (I’ve done it myself), but that is not the design intent of the tool.  So, it would not normally be considered a lever.  If the screwdriver tip does not act as a wedge, i.e. moving two surfaces apart, it should not be considered a wedge.  All of that said, I understand that the average 3rd grader will not grasp the nuances so I generally avoid anything that could be misinterpreted this way.  If I use a screwdriver I will include a picture showing it being used for its original purpose.

Tools such as spatulas which are designed to separate something, say a pancake from the surface of a griddle, could be considered wedges because they are generally held at an angle.

#### What is the total possible points in the 2018 district tournament?

Each test has 100 questions, 10 questions per station.   The first 5 questions (simple machine identification) at each station are worth 1 point each.  All other questions are worth 2 points each.  The total possible number of points for each test is 150 points.

#### Can you explain how a light bulb is a wheel and axle? how about a screwdriver?

The wheel and axle is a device that consists of a wheel attached to a smaller axle so that these two parts rotate together and force is transferred from one to the other.  The center of rotation is the same for both the wheel and the axle.

When a rotating force is applied to the wheel, the axle also turns.  Because the wheel moves through a greater distance than the axle, the axle moves with more force.  The work performed, defined as the force multiplied by the distance, must be the same for both the input and the output.

In the screwdriver, the handle is the wheel, and the shaft which fits into the screw head is the axle.  A screwdriver where the handle is the same diameter, or only slightly larger, than the screw’s diameter would require more effort to turn than one where the handle was much larger.  So, there is a mechanical advantage to using a screwdriver with a handle larger than the shaft.

A lightbulb can be considered a wheel and axle because the force used to screw it into a socket is applied to the globe, which is usually larger in diameter than the screw base.  The force on the globe is transferred to the screw base.  A lightbulb with a large globe will be easier to tighten into the socket than one with a smaller globe.

This is distinctly different from a wheel on a wagon, for instance, where the wheel turns but the axle does not.  In this case the wheel merely serves to reduce or eliminate friction.