A good scale can be a very useful tool. Maximum weights an important factor in the construction of a winning car. The closer you can get to the maximum weight limit, the more potential energy you will have to release. “Cars with more mass can store more Potential Energy to be converted to Kinetic Energy”. It’s the release of that energy that carries you to the finish line. .
Let’s keep all this weight stuff in perspective. Kinetic energy is 1/2 Mv2, so the car with more mass M must also have a slower velocity v for energy to stay constant. A fraction of a gram doesn’t make a huge difference at the finish line but one gram can easily mean the difference between winning and losing because of the high accuracy of race timing devices. If you do the math, 1 gram (0.03 oz) can still makes about 1/8″ difference at the finish line and some race timers measure 10 times closer than this. So, if you are really sloppy with your weight management and go in with a 4 oz car, you can be behind over ½ car length or 4″ at the finish line.
So, what is the actual importance of optimizing weight?
a) It is about the same importance as friction control (lubrication)
b) It is about the same importance as air drag control (streamlining)
c) The person inspecting your car (weighing) thinks it is a lot more important (like Aristotle-Lecture 1) and he is the judge.
d) Its a lot easier to get maximum weight, compared to optimizing a) or b).
Keep in mind – the weight of your car is just 1 more piece of a puzzle that has many interdependent pieces.
Every object with mass that can be affected by gravity has Potential Energy PEg = mgh. If your derby car is in a position to be affected by gravity (resting at the start pin), it has gravitational potential energy. Once the car is in motion it has velocity and the Potential Energy is converted to Kinetic Energy KE = (1/2)mv2, which is the energy of motion. There is a direct relation between gravitational potential energy and the height of an object; the higher that an object raised above the the ground, the greater the gravitational potential energy.