By relativity equations, I presume you mean energy mass equivalence, mass dilation, time dilation and length contraction? If there's more, let me know. Here's a little guide for those four.
Energy Mass Equivalence:
The infamous e=mc². It is saying that energy released is equal to the mass of the object multiplied by the speed of light squared. Any question revolving around this equation I find quite easy. All you have to look for is a mass in kilograms and something along the lines of "How much energy...". Remember energy is measured in Joules. Also, the question can ask you for the mass if the amount of energy is known. i.e. m=e/c². In these types of questions, it will most likely start with "What is the mass of an object...". Any question in this area relies on the knowledge that you know c²=9x10^16 m/s.
Mass Dilation:
This is the idea that at relativistic speeds, all mass is dilated, or becomes larger. This can be rationalised because of F=ma and the fact that you cannot travel faster than the speed of light. The more massive the mass becomes, the more energy that has to be used to give it the same acceleration, making further accelerations more and more difficult. The energy that is put into attempted acceleration is instead converted into mass.
For both dilation equations, the root sign will be in the denominator. This is because √(1-v²/c²) will always be less than 1. Since any number over a number less than one becomes bigger, you can see why any dilation equation is set out the way it is. Remember that the REST MASS goes on the top of the equation, while the velocity that the mass is travelling at goes on the bottom. This will result in a larger mass after you equate. Remember to teach yourself the difference between when a question asks for the rest mass or the dilated mass. If you are given two masses, you must equate the velocity. The larger of the two masses stays on it's own outside the equation, and the smaller mass goes on the numerator. Rearrange as required to find the velocity.
Time Dilation:
Time dilation is much the same as mass dilation in the way the equation is set out. The smaller time becomes the numerator, and the larger time is the object of the equation. Time dilation can be validated by experiments such as flying one synced up atomic clock around the world and leaving another stationary, and also muons entering the earths atmosphere. All the same rules apply to time dilation as to mass dilation. Just make sure the "REST TIME" is in the numerator of the equation and the DILATED TIME is outside the equation.
Length Contraction:
As an object comes close to the speed of light, the length of the object will contract from an external frame of reference. This equation is a little different. It's the only one where the REST LENGTH and the √(1-v²/c²) are multiplied. This is easily explained because as the word contraction suggests, the length gets smaller. As the √(1-v²/c²) is always less than 1, anything multiplied by it will be smaller and not larger. In these equations, the rest mass will be multiplied by the √(1-v²/c²) and the contracted mass will be outside the equation.
I hope those brief explanations help. Remember that all of these equations can be rearranged depending on what the question asks for. Also familiarise yourself with being able to delineate between the rest mass/time/length and the relativistic mass/time/length. If you know the differences between the equations as well as those two little rules, you should be able to attempt any question with much success.
If you have any specific questions you need help with or need something in this comment clarified, please feel free to ask.
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