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Your task is to build a mousetrap powered car, built from wood, paper, plastic, metal, erector sets, pens, rulers, old toys, Legos, or other materials.

We need a fair comparison between race cars. Therefore it must be powered by only 1 mousetrap. You may not modify the mousetrap, such as by over-winding the metal coil, because that would unfairly increase its potential energy storage.

A rat trap, or trap for any other animal, is not safe or acceptable.

2 people may collaborate to make 1 car.

If you do not have your car on the day that it is due, you lose 5 points per day.

I suggest working in groups, making your own local mousetrap racer “factory”. This approach is easier and more fun.

Clearly print your names somewhere on the car!

Dates

Tue Sept. 15 – Introduce the project.

Thur Sept. 24 – Bring in your mousetrap racer, even if not yet complete. Compare your car with the cars made by others. Test it. See what modifications need to be made.

Tue Sept. 29 – Mousetrap racers due today. We will have competitions:

(A) Fastest: Which car goes to the finish line in the shortest amount of time?

(B) Furthest distance: Which car goes the furthest?

Much information on mouse trap racers is available online. However, you may not use a kit to build your racer.

Websites with information on how to make mousetrap cars:

http://www.instructables.com/

http://www.docfizzix.com/help.htm

Gallery of great mousetrap racers. Can-do.com

What is a mousetrap powered car? How does it work?

It is a vehicle powered by a mousetrap spring. We tie one end of a string to the tip of a mousetrap’s snapper arm, and the other end of the string has a loop that is designed to “catch” a hook that is glued to a drive axle. Once the loop is placed over the axle hook, the string is wound around the drive axle by turning the wheels in the opposite direction to the vehicle intended motion.

As the string is wound around the axle, the lever arm is pulled closer to the drive axle causing the mousetrap’s spring to “wind-up” and store energy. When the drive wheels are released, the string is pulled off the drive axle by the mousetrap, causing the wheels to rotate.

How do you build a mouse trap powered racer?

There is no one “right way” to build a mousetrap powered vehicle. The first step to making a good mouse trap powered car is simple: put something together and find out how it works.

Once you have something working you can begin to isolate the variables that are affecting the performance and learn to adjust to improve your results. You build, you test and experiment, you change, and you do it all over again.

What’s the difference between a FAST Racer and a LONG distance traveler?

When you build a mouse-trap car for distance, you want a small energy consumption per second or a small power usage. Smaller power outputs will produce less wasted energy and have greater efficiency. When you build a vehicle for speed, you want to use your energy quickly or at a high power output. You can change the power ratio of your vehicle by changing one or all of the following:

* where the string attaches to the mouse-trap’s lever arm
* the drive wheel diameter
* the drive axle diameter.

The amount of energy released by using a short lever arm or a long lever arm is the same, but the length of the lever arm will determine the rate at which the energy is released and this is called the power output.

Long lever arms decrease the pulling force and power output but increase the pulling distance.

Short lever arms increase the pulling force and the power output by decrease the pulling distance but increasing the speed.

Building for speed

If you are building a mouse-trap car for speed, you will want to maximize the power output to a point just before the wheels begin to spin-out on the floor. Maximum power output means more energy is being transferred into energy of motion in a shorter amount of time. Greater acceleration can be achieved by having a short length lever arm and/or by having a small axle to wheel ratio.

Building for distance

Minimize the power output or transfer stored energy into energy of motion at a slow rate. This usually means having a long lever arm and a large axle-to-wheel ratio.

If you make the lever arm too long, you may not have enough torque through the entire pulling distance to keep the vehicle moving, in which case you will have to attach the string to a lower point or change the axle-to wheel ratio.

Supplies

Most parts can be scavenged from toys, or recycled materials. You may also consider stores such as Michael’s Art Supply, Home Depot, or A. C. Moore. Mousetraps are available in 2 packs, for less than $2, from supermarkets.

Learning Standards

2016 Massachusetts Science and Technology/Engineering Curriculum Framework

HS-ETS4-5(MA). Explain how a machine converts energy, through mechanical means, to do work. Collect and analyze data to determine the efficiency of simple and complex machines.

HS-PS3-3. Design and evaluate a device that works within given constraints to convert one form of energy into another form of energy.
• Emphasis is on both qualitative and quantitative evaluations of devices.
• Examples of devices could include Rube Goldberg devices, wind turbines, solar cells, solar ovens, and generators.

Appendix VIII Value of Crosscutting Concepts and Nature of Science in Curricula
Cause and Effect: Mechanism and Explanation. Events have causes, sometimes simple, sometimes multifaceted. A major activity of science and engineering is investigating and explaining causal relationships and the mechanisms by which they are mediated. Such mechanisms can then be tested across given contexts and used to predict and explain events in new contexts or design solutions.

College Board Standards for College Success: Science
Standard PS.1 Interactions, Forces and Motion
Changes in the natural and designed world are caused by interactions. Interactions of an object with other objects can be described by forces that can cause a change in motion of one or both interacting objects. Students understand that the term “interaction” is used to describe causality in science: Two objects interact when they act on or influence each other to cause some effect. Students understand that observable objects, changes and events occur in consistent patterns that are comprehensible through careful, systematic investigations.

Next Generation Science Standards: Science – Engineering Design (6-8)
• Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.

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