To clear up a misconception: a Newton Car is not a Pinewood Derby car, but it could be a mouse trap car. A Newton Car is a test platform to demonstrate Newton’s 2nd Law of Motion.
What it is . . is Physics. Ouch!
This is commonly a middle school/junior high science project testing the students critical thinking, ability to form a hypothesis, and test to it.
But first a review: Newton had 3 Laws of Physics.
1: An object at rest will stay at rest unless an external force acts upon it.
2: Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object.)
3: For every reaction there is any equal and opposite reaction.
A digression: Whenever I think of high school science class I recall that we use to say that if its green and wiggles, its biology; if it stinks, its chemistry; and if it doesn’t work, its physics.
Back to the Newton car. Basically you’re making a slingshot: two dowels on opposite ends of the front of a block of wood; one dowel located dead center in the rear. A string attached to the rear dowel, holding a rubber band in the “ready” position until the string is cut.
Cutting the string will cause the rubber band to launch its payload, which can be a 35mm film canister or a pill bottle. Depending on what’s loaded in the bottle will determine how far the car will be propelled in the opposite direction.
They’re not going for distance: they’re testing to see how far differently weighted bottles (i.e. mass) will travel. Also what happens when more than one rubber band is used for propulsion. (post hoc, ergo proctor hoc. . . . couldn’t resist).
Oops! I got ahead of myself: we forgot the wheels.
For this you could use wheels from a pinewood derby car. Use a 1/8 inch brass tube as a bearing to hold the 3/32 inch axle. Attach the assembly to the bottom of the block of wood using 1/8 inch nylon landing gear straps. To attach the wheels, use 3/32 inch wheel collars on either side of the wheels. The inside collar acts as a standoff; the outside collar keeps the wheel from falling off.
Sketch courtesy of NASA