Physical Science
Can Weight be a Bad Thing? The Other Side of Added Grams by Emile Abed
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et me introduce myself, I’m a Physics teacher with an engineering background and teach 11 – 18 year olds in the UK the wonders of the physical world. This doesn’t make me a diecast guru but I do have a nerdy interest in making sense of one of world’s most chaotic sports. The first things most of us do to try and make our cars go faster is to increase the weight. This is because when trying to make anything go fast you want the forward force, in this case the weight, to be as high as possible giving you enough acceleration to only ever see your fellow competitors as everdecreasing dots in your rear view mirror. What would you say if I told you weight makes no difference to acceleration? You’d think I’m crazy. But if there is no friction this is true. If you’ve ever watched the grainy footage of an astronaut dropping a feather and a hammer on the moon you see them both hit the ground at the same time. There’s a much clearer video of Professor Brian Cox doing something
similar in a giant vacuum chamber with a bowling ball and feathers. Without air resistance everything drops with the same acceleration. It all seems unreal as we only ever experience objects traveling through air. So what does this mean for diecast cars going down fig. 1 – Weight raises the centre of gravity of a vehicle. How it is positioned can have an effect on your speed. the track? Is weight as where a student normally turns important as it seems and, to really round and shouts, “Hang on a turn things onto its roof, can weight minute, that means a heavier car has slow you down? more energy that’s why it’s faster!”. But it takes more energy to move a Now, I can’t go through a Physics car with more weight. If you do the “lesson” without talking about calculations, when all the energy. With diecast racing we gravitational energy is converted into normally start with gravitational kinetic energy, a change in the mass energy, the stored energy of a object has no effect on final speed. (Don’t at a height, and we want this all to worry I’m not going to bore you with turn into kinetic energy, the stored calculations here!) energy of a moving object. Now, I could tell you weight makes As all the cars start at the same no difference and give your height the only variable that effects (Heavy Science cont. on page 14) its energy is the weight. This is
September 1, 2020 | 7
