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In order to solve any physics problem you must know which equation to use. Writing down all of the known information is the first step to finding the right equation. If you know values for the distance, time, and acceleration, you can use the following equation:  Initial velocity: Vi = (d / t) - [(a * t) / 2]  Understand what each symbol stands for.   Vi stands for “initial velocity”  d stands for “distance”  a stands for “acceleration”  t stands for “time” Once you have written the known information and determined the proper equation, you can fill in values for the appropriate variables. Carefully setting up each problem and writing out every step of the process is important. If you make a mistake, you can easily find it by looking back at all of your previous steps. With all of the numbers in place, use the proper order of operations to finish the problem. If you’re allowed, use a calculator to limit the number of simple math mistakes.  For example: An object accelerating west at 7 meters (23.0 ft) per second squared traveled a distance of 150 meters (492.1 ft) within 30 seconds. Calculate the initial velocity of that object.  Write the known information:  Vi = ?, d = 150 m, a = 7 m/s2, t = 30 s   Multiply the acceleration and time. a * t = 7 * 30 = 210 Divide the product by two.  (a * t) / 2 = 210 / 2 = 105 Divide the distance by the time. d / t = 150 / 30 = 5 Subtract your first quotient from the second quotient. Vi =  (d / t) - [(a * t) / 2] = 5 – 105 = -100 Vi = -100 m/s west Write your answer correctly. Include a unit of measurement, usually meters per second or m/s, as well as a direction the object was traveling in. Without providing information about the direction, you only have a measurement of speed rather than velocity.
Know the right equation to use. Fill in the known information. Solve the equation.