Three Fundamental Equations

[Baoying Li 1B]

When you are solving a problem, how do you know which fundamental equation you are using? What are some keywords in the problems that may help? For example, E =pv, hv, hc/wavelength.

[Vanessa Chuang 4F]

It would really depend on what the question has given you. For example, if the question gives you mass and velocity, then you will most likely use E=pv because none of the other equations need mass and velocity as an input. This would work similarly for other questions that give only certain values (such as wavelength or frequency). Basically, there aren't really any keywords to look for-- just pay attention to what values are given to you and what units those values are associated with.

[Nare Nazaryan 1F]

It can be a little tricky, but it all depends on what is given. If you are given frequency and need to find wavelength, for example, you can use c=wavelength*frequency and just adjust the equation to what you're trying to solve. Some problems will ask you for an answer after you go through a few different equations if you can't get to the answer with just one.

[Kishan Shah 2G]

The way I decide which equation to use is that I first write down all the formulas on a separate piece of paper in front of me. Then under the problem, I write down all my given values. Then I look at what value the question is asking for. Then it is easier to determine which equation(s) to use to get to the write answer based on whats given to you. Also make sure to know what each variable in each equation means very well.