Pine Wood Derby Fun Facts and Tips 5 Steps to a fast Pinewood Derby Car.

Make sure that your car is exactly 5oz.

Physics Explanation: The reason you want your car to be the maximum allowed weight (mass) is because you want to maximize your cars potential energy. Your car will have the same power source as every other car. GRAVITY. Potential energy is defined by the following formula E = m * h. Or in other words Potential Energy is equal to the mass/weight times the height. If you took a 3 pound weight and dropped it on your foot from 4 inches it would not hurt much. But if you took that same 3 pound weight and dropped it from 10 feet it would most likely break your foot. The reason is because there is much more energy being produced by a ten foot drop than there is from a 4 inch drop. In order to obtain the most potential energy out of your car you need to make sure it has the maximum mass allowed.

Add weight to your car towards the back rather than the front.

Physics Explanation: The center of mass on your car will again affect the potential energy of your car before the race even begins. Remember E = m * h from the previous step? Well the h or height is really based on the center of gravity for your car. For example: If you finish your car and try to balance it on one finger. The spot that you are able to balance the car is the center of gravity for the car. The closer that balance point is to the back of the car the better. You don't want the car to do wheelies down the track because that will cause other speed problems but you do want the weight to be more towards the back of the car than the front.

Debur, sand and wax the wheels.

Debur the wheels. Take off the flashing and seam that was produced when the wheel was molded with a 600 grit or better sandpaper. Inside as well as out. Sand any bumps off the wheel the sandpaper. Metal polish will restore the gloss. Be careful not to break any rules your race has regarding wheel modification. (Narrower wheels have less friction and are better, but often disallowed). Don't sand too much or you'll create a flat spot. Sand by hand not in the drill. Heat from the high speed of a drill will damage the plastic wheel. Wax the wheels with furniture polish. Make sure the polish does not contain a solvent of any sort. Physics Explanation: See Friction Section Below

Polish the Axles

Polish the axles. First with a 400 grit if you have a really bad spot. Then a 600 grit, and then a jewelers rouge. Finish off with a chrome/metal polish. Physics Explanation: See Friction Section Below

Have 3 wheels touching the track.

Have only three wheels touching the track. Raise a front one slightly. There is less total friction with 3 wheels rolling than 4. There is not less total friction between the wheels and the track. But there will be less probability for friction loss between the wheels and the side of the car Physics Explanation: See Friction Section Below

Taper The Axles 15 degrees for less friction loss.

The head of the axle should be tapered about 15 degrees so it rubs against the wheel less. Physics Explanation: See Friction Section Below FRICTION: The number one cause for losing pinewood derby cars is friction. The car with the least friction will usually win the race because of it's relationship to acceleration. We know that most of the cars will have the maximum allowed mass or weight 5 oz. We also know that every car will start from the same height. We know that Gravity will be the same for each car so the car with the least amount of friction usually wins the race all other factors being equal. The 3 areas that friction occurs is between the wheels and the track, the wheels and the axles, and the wheels and the side of the car. Acceleration = Force / Mass The quantity g is often called the acceleration due to gravity = 32ft/s^2 Friction = frictional coefficient * Normal Force N or Normal Force In particular, a mass of weight w = mg on an inclined plane at an angle theta (the angle of the track will be the same for every car) Force = mass * gravity The coefficient of friction (static or kinetic) is a measure of how difficult it is to slide a material of one kind over another; the coefficient of friction applies to a pair of materials, and not simply to one object by itself. Mass = force / acceleration Friction = frictional coefficient *mass * gravity By substituting mass with force / acceleration we get Friction = frictional coefficient * (force / acceleration) * gravity By multiplying both sides of the above equation by acceleration we get Friction * acceleration = frictional coefficient *force *gravity By dividing the above formula by Friction we get Acceleration = (frictional coefficient * force * gravity)/friction All of the formulas above show the relationship between acceleration and friction. If you increase friction without in the above formula your acceleration will decrease. Which means if you decrease friction you will increase acceleration.

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