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Tutee Problem-Solving Skills

These guidelines can be very useful when solving physics problems. Most people have an intuitive feel for physics in everyday life; for instance, most people can catch a softball. What physics does is allow us to describe the motion of the ball analytically: to determine how long the ball was in the air, or how fast it was thrown. Thinking about the questions you are asked in terms of real world experiences you are familiar with can be very useful, as can many of the tips listed below.

Read the problem carefully – Think about what is happening. Try to identify the concepts you have used before and see where they apply. This problem may be about objects falling due to gravity, or about masses on springs, or about circular motion, or even some combination of concepts. Regardless, identifying the concepts will help guide your problem solving and show you where to look in the textbook or other references for similar problems.

What are you trying to solve? – Almost all physics problems are word problems. Learn to interpret the words to discover what you are being asked to analyze. “How long does it take?” usually means you are trying to find the time. “How fast is it moving?” usually means you are trying to find the velocity. “How far?” or “where does?” usually mean you are trying to find the distance.

Solve equations algebraically first – In most cases, it is far easier to solve the equation(s) algebraically, and then put in numerical values. For instance, if you were told that a force of 18 N was applied to an object with a mass of 3 kg, and asked to find the acceleration, you might start with the equation

F = ma and then solve for the variable in question (acceleration), giving you

a = F/m now that you have solved the equation, put in numbers

a = (18 N) / (3 kg) = 6 m/s2

Analyze your units – Remember that you can only add quantities when the units are the same. For instance, you can add the mass of one object to the mass of another. But you can’t add the mass of one object to a force. Be sure that when you multiply units, the dimensions work out properly. Using the example above,

[F] = N = kg * m / s2 and [m] = kg so,

[F/m] = N/kg = ( kg * m / s2 ) / kg = ( kg * m ) / ( kg * s2 ) = m / s2

which is the units we expect for acceleration

Does your answer make sense? – In most of the problems, the numerical values given are realistic numbers. So, if you are asked to find the velocity of a car, and the answer is a few tens of meters per second, this seems reasonable. If the answer you get is hundreds of meters per second, or only centimeters per second, these values are probably wrong. Occasionally, you will be asked to find values in more extreme circumstances; for instance, the acceleration a motorcycle has when it crashes into a semi truck would be enormous. In this case the value of the answer is extreme, but so is the situation. As you do your homework problems, try to learn which values are reasonable, and which are extreme. This will help develop your physical intuition and guide you on future problems.

Remember what happened during lab experiments and lecture demos – One of the major goals of physics lab experiments is to help you develop a feel for what real world situations are like. By performing those experiments you can gain valuable insight into the results you expect when solving physics problems. Try to think back on your results in the lab (the labs often cover material before you reach it in the lecture course) and see if the answer you are getting now is reasonable, based on your results during the lab. The same is true of the demonstrations done during lecture.

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