1.14 : Solving Problems in Physics

In physics, the problem-solving process can be facilitated by considering three general steps.

Step one, strategy. Make a list of what is given in the problem statement, identify the unknown to be determined, and determine which physical principle will help you solve it.

For example, a car makes one round trip around a 400-meter circular track in 1 minute 20 seconds. Determine the average speed and average velocity of the car.

Let's begin with the known quantities. We know it takes 1 minute and 20 seconds for the car to make it around the 400-meter track, which gives time and distance quantities.

We need to determine the unknown quantities—average speed and average velocity.

Step two, solution. The next step in the problem-solving process is to find the solution. Use the appropriate equation, substitute the known quantities, and obtain the numerical solution.

The average speed of the car is given by the total distance divided by the total time taken to cover the distance.

That is 400 meters divided by 1 minute 20 seconds. The quantity of time should be converted into its basic unit, seconds, before performing the calculation. Therefore, the average speed of the car equals 400 meters divided by 80 seconds, which is 5 meters per second.

The average velocity is given by total displacement or change in the position of the car divided by total time taken. Since the initial and final position of the car is the same, the total displacement is zero, giving the average velocity of the car as zero.

Step three, evaluation. The final step in the problem-solving process is the evaluation of your answer. Check the units of the obtained answer and reconsider things if there's a discrepancy.

Here, meters per second is the unit of the obtained answers, which corresponds to the quantities, speed and velocity. We have used the concepts of displacement and speed to solve the problem correctly.