Your task is to build a mousetrap powered car!

It can be built from wood, paper, plastic, metal, erector sets, pens, rulers, old toys, Legos, and 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!

Giving time to do this

Day 1 – We introduce the project, discuss the physics and engineering principles, show some videos and photos.

Day 2 – (Which could be any day that fits our class schedule) – Have students bring in the building materials they have procured so far. Also, as a teacher I will help make materials available in class. Both teacher and some volunteer students will show in class how to assemble a mousetrap racer. The way that it is shown in class is not the only way to do it.

Day 3 – Classroom build. Students individually or in pairs work on the mousetrap racer. First start off with a brief review of physics principles – storing energy as PE, simple machines, how mechanical devices can transform PE into kinetic energy, etc.

Day 4 – Run the mousetrap racers! Find a long hallway with a smooth floor. 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.

Instructables (several ideas here)

Mousetrap cars and kits from Doc Fizzix. Great for ideas

Gallery of great mousetrap racers. from UCI Summer Science Institute

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.

Build, test, have fun spectacular failures, and improve, just like SpaceX rockets.

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.

We change the power ratio of a 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

Next Generation Science Standards

DCI – Energy is a quantitative property of a system that depends on the motion and interactions of matter and radiation within that system. That there is a single quantity called energy is due to the fact that a system’s total energy is conserved, even as, within the system, energy is continually transferred from one object to another and between its various possible forms.

 Conservation of energy means that the total change of energy in any system is always equal to the total energy transferred into or out of the system.

 Energy cannot be created or destroyed, but it can be transported from one place to another and transferred between systems.

 Mathematical expressions, which quantify how the stored energy in a system depends on its configuration (e.g., relative positions of charged particles, compression of a spring) and how kinetic energy depends on mass and speed, allow the concept of conservation of energy to be used to predict and describe system behavior.

 The availability of energy limits what can occur in any system.

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.

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.