CO2 Cars Project #2 Land Transportation

Objectives By the end of the unit, the students will be able to: State what Friction and Rolling Friction are State how aerodynamics plays a role in the performance of your car State how weight plays a role in the performance of your car Demonstrate how wheels play a role in your projects success by using the wind tunnel State what Thrust, Drag, Gravity, and Lift are Demonstrate how to Construct a CO2 car that will travel 50 feet in under 1.5 seconds

What is Rolling Friction? Answer: Rolling friction is caused primarily by the interference of small indentations formed as one surface rolls over another.  This is the idea behind the frictional forces involved with wheels, cylinders, and spheres.  http://www.fearofphysics.com/Friction/friction.html

What is Friction? Friction is the "evil" of all motion. No matter which direction something moves in, friction pulls it the other way. Move something left, friction pulls right. Move something up, friction pulls down. Friction is actually a force that appears whenever two things rub against each other. Although two objects might look smooth, microscopically, they're very rough and jagged. As they slide against each other, their contact is anything BUT smooth. They both kind of grind and drag against each other. This is where friction comes from. But friction is not all bad. In fact, it has a lot to do with life as we know it here on Earth. Without it, we wouldn't be able to walk, sit in a chair, climb stairs, or use a mouse to surf the web.

What is Aerodynamics? Aerodynamics is the study of how air flows under, over, and around an object. Thinking about how aerodynamics will play a role in your vehicles in the design stage will help your vehicle to do better. It is important to think about all aspects of aerodynamics that could affect your project such as the wheels. You might want to use the small wheels or carve out the middle of your car and tuck the wheels inside.

Weight of the car matters! Although you might not think it, the weight of the car matters for the performance. The lighter the vehicle the less friction it will have and the more thrust will be the result. Although taking off too much weight will result in a brittle vehicle that will explode on impact at the end of the track.

Thrust, Drag, Gravity, Lift There are 4 forces that affect everyone’s vehicles and their performance: Thrust: Pushing Forward Force Drag: Pulling Back Force Gravity: Pulling Down Force Lift: Pushing Up Force You have to take into account each force and to try to figure out how to use some and decrease others. For example, you want your initial thrust to be strong so it is important your vehicles front wheels stay on the ground. The smoother your paint job and sanding job the less friction and drag. The lighter your vehicle the less mass it will have.

Challenge Part 1 is that each student will design, sketch, and construct their own CO2 Cars using various materials and equipment in the Construction Lab. The Sketches are random ideas of your thoughts but there are a minimum of 4. From those 4 sketches select 1, draw it in detail using a ruler and straight lines (no freehand drawing). When drawing your initial drawing place the block of wood on its side and trace it onto a piece of paper. Then stand the block up and trace the bottom onto another piece of paper. Inside those lines is where you draw your vehicle. When done you cut out the traced block pattern and tape it onto your block of wood. When firmly placed on your block of wood mark for your axles and drill both axle holes first. Next you start cutting out your designs cutting through the paper and the wood. There is a poster hung on the wall that gives ideas of different cars.

Challenge Part 2 is each student will be provided with one pre drilled wood blank to ensure accuracy. After you have cut out and sanded your wood blank into a car we will put it in the wind tunnel. Keep testing using the wind tunnel before testing day. You want to have the lowest possible drag score which is measured in ounces. On testing day your test result will be less than .40 oz drag.

Challenge Part 3 is you will be performing a roll test which is done without a CO2 cartridge in your vehicle. You will be placing your car on a ramp and letting it roll down. Your car must stay within a 1 foot wide span for 6 feet. This is called a roll test and tests for accuracy of alignment.

Challenge Part 4 deals with the time trial. Your vehicle will travel the full distance of 50 feet in under 1.6 seconds. Your vehicle must be the full width of the wood blank at the front axles and rear axles.

Procedures Brainstorm ideas and sketch 4 of them onto 2 pieces of paper Choose a design that you like the best, draw an initial drawing of it with dimensions Use the supplied materials to create the energy launcher Finish the energy launcher using a filler and any color paint you choose or vinyl

Evaluation Project Travels more than 30 feet Project travels 15 feet in under 6 seconds Project travels up ramp 10 or more feet Project looks like Initial Drawing with minimal changes Student shows above average effort Student shows above average safety skills 100 Points

Evaluation Project Travels more than 30 feet Project travels 15 feet in under 6 seconds Project travels up ramp 10 or more feet Project looks like Initial Drawing with moderate changes Student shows above average effort Student shows above average safety skills 75 points

Evaluation Project passes 2 of 3 challenges Project looks like Initial Drawing with very noticeable changes Student shows above average effort Student shows above average safety skills 50 points

Evaluation Project does not work Project does not look like drawing at all Student shows no effort Student not allowed in class if not demonstrating proper safety skills 0 points