MOUSETRAP CAR DESIGN

MOUSETRAP CAROBJECTIVES:The student will be able:• To demonstrate proper and safe procedures while working with

technological tools, apparatus, equipment, systems and materials.• To exhibit positive human relations and leadership skills.• To demonstrate and apply design/problem-solving process.• To develop the idea that technology is the application of

knowledge to solve human problems and extend capabilities.• To learn Newton’s three laws of motion.• To design and construct a mousetrap car using the program

requirements/ guidelines.

Warm Up Discussion QuestionsDiscuss these questions with your team members and write

your answers on a sheet of paper:1. What are Newton’s Three Laws of Motion?2. How is Kinetic Energy used in today’s society?3. Explain how Mechanical Technology applies to Mousetrap

cars.4. List and explain five applications of Mechanical Technology

(other than mousetrap cars).5. What is Friction?6. How can friction cause your Mousetrap car to slow down?7. What is the law of conservation of energy?

WHAT IS A MOUSETRAP CAR?• A mousetrap car is a small vehicle having only

one form of motive power being from a mousetrap. Variations include the use of multiple traps, or very big rat traps, for added power.

• Mousetrap cars are very often used in physics or other physical science classes to help students build problem-solving skills, develop spatial awareness, learn to budget time, and practice cooperative behavior.

VOCABULARY• KINETIC ENERGY– Kinetic energy is energy of motion. The kinetic energy

of an object is the energy it possesses because of its motion. The kinetic energy* of a point mass m is given by: Kinetic Energy = ½ mv²

• FRICTION– Friction is a force. It is a force that slows motion and

dampens energy. When wind blows through a tree the tree impedes the wind flow. No matter which direction something moves in, friction pulls it the other way.

VOCABULARY• NEWTON'S THREE LAWS OF MOTION– Newton's First Law of Motion "Law of Inertia":

Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

– Newton's Second Law of Motion: The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. In this law, the direction of the force vector is the same as the direction of the acceleration vector.

– Newton's Third Law of Motion: For every action there is an equal and opposite reaction.

VOCABULARYLAW OF CONSERVATION OF ENERGY– The law of conservation of energy is that energy

cannot be created or destroyed, but it can be transferred or transformed from one form to another (including transformation into or from mass, as matter). The total amount of energy in a closed system never changes.

DESIGN CONCEPTS• Wheel-To-Axle Ratio - For distance, use large wheels

and a small axle. Think of the rear wheel of a bicycle; a small drive gear and a large wheel.

• Inertia - How much energy does it take to get your car started? A lighter car requires less. Lower the mass of your vehicle for best distance.

• Rate of Energy Release - If the energy is released slowly, the power is used more efficiently, and the car will travel further. One way to slow this release is to lengthen the lever arm. A longer arm travels a greater distance and allows more wraps of string around the axle. The car will go far, but more slowly.

DESIGN CONCEPTS• Friction - Minimize friction on the axle by minimizing

the contact surface area. A thin steel bracket was used in this example. At first a hole drilled through a wood block was used to hold the axle. This was abandoned because the larger surface area causes to car to use energy overcoming friction rather than traveling forward.

• Traction - This is what you call friction when it is used to your advantage. Friction should be maximized where needed (where the string wraps around the axle and where the wheels contact the floor). Slipping string or wheels equals wasted energy.

ASSIGNMENTSDesign PlanBrief Constructed ResponsesDaily Laboratory JournalPresentation/Demonstration

Design Plan • Design Plan must include:– A list of materials used (should be numbered)– A diagram of your catapult. The diagram should

have all dimensions labeled (including units) and should be neatly drawn. Your diagram should be drawn on plain white paper and should fill most of a single page.

– A plan that outlines your design process, mistakes, and outcomes. (2 pages)

BRIEF CONSTRUCTED RESPONSE #1

• Students must view the video (http://www.youtube.com/watch?v=haannJ_7w-k) and respond to the following prompt:

Explain how Kinetic Energy could be used in society to conserve non-renewable energy

(gas, coal, electricity, etc.) Write about your design idea and how it is to be used.

List positive impacts your design would have on society.

BRIEF CONSTRUCTED RESPONSE #2

• Students must view the video (http://www.youtube.com/watch?v=iH48Lc7wq0U) and respond to the following prompt:

Apply Newton’s Laws of Motion to a moving car. Explain how all of Newton’s three laws

apply to a moving vehicle.

BRIEF CONSTRUCTED RESPONSE #3

• Students must view the videos (http://www.youtube.com/watch?v=jVMEclmIQss and http://www.youtube.com/watch?v=Hqc9uexNL64) and respond to the following prompt:Compare and contrast the design of your

car to the cars displayed in the video. Explain how your car design works and

how it will succeed in moving.

Daily Laboratory Journal Entries

• Students’ Daily Laboratory Journal Entries Must Include:– Journaling must include a record of the entire

investigatory process, from concept to conclusion. – Each time the student makes an entry into the

journal, the date and time should be recorded. Nothing should ever be erased from a journal.

– This is the process by which students gain an understanding of the objective of the lab, what variables are involved, what response they are looking for, and how they intend to measure that response.

PRESENTATION/DEMONSTRATION

• Students’ Presentation/Demonstration includes:–Report should be neatly typed or written

and sections should be well marked.–All concepts are presented in complete

sentences excluding the list of materials which may be numbered.

GRADING RUBRICSContributions - Routinely provides useful ideas

when participating in the group and in classroom discussion.

Attitude - Always has a positive attitude about the task(s).

Working with Others - Almost always listens to, shares with, and supports the efforts of others.

Quality of Work - Provides work of the highest quality.

Preparedness - Brings needed materials to class and is always ready to work.

MOUSETRAP CAR BUILDING INSTRUCTIONS:

• Assemble the chassis. This platform will serve as the base for the mousetrap, the wheels and any gearing mechanisms that you may use in your mousetrap car design. Use lightweight pieces of wood and install eye hooks as axle carriers.

• Mount the mousetrap onto the chassis. Screw the mousetrap to the chassis. The spring mechanism on the mousetrap serves as the power for the car.

MOUSETRAP CAR BUILDING INSTRUCTIONS:

• Build your wheels out of lightweight materials, such as foam board, or use old CDs. Attach rubber bands, balloons or other rubber material as tread. Make sure to use large wheels relative to the axle size.

• Install the wheels and axles. Axles can be wooden dowels, or plastic or metal rods. Be certain they are straight and balanced, or your mousetrap car may shake itself apart.

MOUSETRAP CAR BUILDING INSTRUCTIONS:

• Attach the drive string to the mousetrap. Leave the end of the string that you will wind around the drive axle loose so that it releases when it reaches the end. If you don't leave the end of the string loose, it will start to rewind at the end of its travel and slow down the car.

• Lock down the trap and wind the string around the drive axle. Release the trap to send your mousetrap car down the road.

Read more: Http://www.ehow.com/how_2044833_build-mousetrap-car.html#ixzz1CAw2NXfU

MOUSETRAP CAR EXAMPLES

MOUSETRAP CAR EXAMPLES

MOUSETRAP CAR EXAMPLES

MOUSETRAP CAR EXAMPLES

MOUSETRAP CAR EXAMPLES

MOUSETRAP CAR EXAMPLES

MOUSETRAP CAR EXAMPLES

MOUSETRAP CAR EXAMPLES

MOUSETRAP CAR EXAMPLES

MOUSETRAP CAR EXAMPLES

CONSTRUCTION TIPS• If the string is just wrapped around the axle, the car may

barely move. Adding a larger drive hub can improve pulling power. In some images there is a rubber tire on the axle, this acts as a "gear" and reduces string slippage.

• Reduce friction on the axle by minimizing the surface area of the support that contacts the drive axle. An axle support of thin steel has less friction than a hole drilled through a wood block.

• Increase friction where it is needed by using a rubber tire or tape around the axle where the string is wrapped. The string should turn the axle and not slip.

• Increase friction by waxing the string with candle wax. By waxing it, the string has better pull on the axle.

CONSTRUCTION TIPS• Reduce mass by using a simple light stick for the body

section. Reducing the mass also reduces the friction at the axle supports.

• Use the longest lever available to extend the mouse trap arm as far as possible. The tip traverses a greater distance allowing more wheel wraps of string to play out. An antenna from a broken boom-box was used for the lever. Anything long, light, and not too flexible will work for the lever.

• Reduce friction by applying lubricant to the axles, wheels, and mouse trap spring.

• Reduce shock by using a bit of sponge as simulated cheese. This reduced the car hopping as the lever arm slapped home.

CONSTRUCTION TIPS• The alignment of the axles and mounts is critical to reduced

friction and increased performance.• Take a CD and the axle with you to the hardware store if

you buy a washer. This may help you to get the right size the first time.

• Create a long and light "body" for the car. The trap and the wheels are attached to this "stick". As seen in the pictures, the body can be smaller than the mousetrap. Trim it down; the lighter the frame the better! (But form boards break more often than boards)

• When situating the trap, make sure the spring is facing the correct direction so the lever arm rotates forward. Ensure the trap is as far forward as possible without touching the front wheels. The longer distance between the trap and the wheels, the better! (To a certain point.)

CONSTRUCTION TIPS• The wheels are a determining factor for a distance car. The

front wheels don't matter in size or number; you can even have just one. As for the back wheels, you want the back wheels to be as large as possible, and the back axle to be as thin as possible. Old CD's work fairly well. A plumbing washer may be used to reduce the hole size in the middle of the CD (to fit the axle better).

• To create traction, cover the wheels with tape, rubber bands, or balloons. If they slip, energy is being wasted. Adding tape to the rear axle may reduce slippage of the string. 5

• To attach the mousetrap to the frame, use glue instead of bolts. The glue will hold just as well and the bolts just add weight! Make sure you have optimum placement of everything before gluing. A screw may give you a chance to change your mind, where as glue is more or less permanent.

CONSTRUCTION TIPS• The keys to obtain maximum distance: reduce weight,

reduce axle friction, and use a long lever for the best mechanical advantage. Use a small diameter axle and large diameter wheels. Each time the axle turns around, so does the wheel. A larger wheel means the car travels further with each turn of the axle.

• The tip of a long lever travels a greater distance than the original bar of the trap. This increases the length of string used, and conserves energy (slows the snap of the trap). The car moves slowly, but it travels farther because spring power is used more efficiently.

READY…SET…GO!

LET’S START BUILDING!!!!!