Answer:
You must catch the known-variables and the unknown-variables from the question to use the right equation.
Explanation:
Whenever you are solving a numerical, follow these steps:
1. From the asked question, jot down the given variables like initial velocity, total time, or acceleration etc.
2. After that, write the variable which is asked and put a question mark next to it.
3. Now that you have the given information and asked information in terms of variables, you should see which equation has all those variables. It might be helpful to jot down all three equations of motion on a side of paper. Once you have all three equations in front of you, you can easily spot the equation which has all the known and unknown variables in it.
Note: Sometimes, you might have to use more than one equations to get to the asked variable. You can think of that as two question instead of one, where you have to find out two variable instead of one.
