How do scientists figure out things like the effect of adding fuel to fire? Can they measure ahead of time like 1 cup of gas = 5 mins of burn time at 500°?
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In this particular case, it’s basically just accounting work. Glossing over the chemistry part of it; fuel has a certain energy content, so if you have a desired rate of energy you want out of the reaction, then you know how fast you have to add fuel, and if you know how much fuel you start with you can figure out how long you can operate.
Beyond that it’s just accounting for inefficiencies and predicting the products.
It depends on the context. It’s straightforward to calculate how much energy will be released in total, but the rate at which it will be released can be more complicated. If you are talking about, say, a specific internal combustion engine, it’s just a matter of doing experiments (or looking up the data from past experiments) and doing some interpolation. If you’re talking about throwing something on a fire, then it is going to depend on what state the fire and the fuel are in to begin with. A lot of rich mathematics has been developed to model fires (e.g. google “activation energy asymptotics”).
Well, first of all, sometimes they can’t. Chaos theory came into existence due to the inability to predict certain results due to their sensitivity to initial conditions. For example, determining exactly how much fluid will go through most hoses in a certain amount of time. Turbulence combined with the unpredictable curve of the tube makes it surprisingly hard to predict.
However, usually it works something like this.
A scientist wants to know exactly what will happen if they add certain amounts of X to a situation. X can be anything from adding fuel to adding heat to anything you can think of that you can add or subtract. So they add different quantities of x and see what the result is.
Usually, there is a pattern. Simple linear patterns are some of the easiest. You add one unit of X and you get Y. If you have two units of X you get two units of Y. And so on.
Other times the pattern might be logarithmic. You add more energy to an object approaching the speed of light, and it goes faster. However, the closer it gets the speed of light. The more energy is required. This creates a logarithmic curve. You can use this curve to determine how much energy it takes to get to any particular fraction of the speed of light, and also see that no amount of energy short of infinity will actually get you there.
Scientists call these patterns laws. Many people think that laws are what you get if a theory has been proven, but they aren’t. Laws are what are observed. Theories are about what causes the law to work that way.
Once you have the law, you can use it to make predictions. That is how scientist and engineers can figure these things out without actually having to do the experiment.
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