Steps in Physics Problem-Solving Method

Steps in Physics Problem-Solving Method
Here is a modified version of the problem solving method as described by the U. of Minnesota
Physics Education group.
1. Focus the problem: Develop your own, qualitative (i.e. conceptual) description of the problem.
What is the physical situation and what do you need to figure out? First visualize the events
taking place in the problem, using sketches where appropriate. Write down in your own words a
simple statement of what it is you need to find out. Write down a list of physics ideas that might
be relevant and describe an approach you think you might be able to use. The point of all this is
to get the problem straight in your own mind, and further to communicate the problem to the
grader or anyone else who may need to know what the problem actually is. When you finish this
step, you should never have to look back at the problem statement again because it will be
2. Describe the physics: In this step you should use your qualitative understanding of the
problem to plan a quantitative solution. First, simplify the problem by describing it with (another)
diagram involving simple physical objects and essential physical quantities. The objects could be
the parts of a physical system, such as blocks, wheels, pulleys, etc. The quantities could be
forces or velocities or energies, etc. Then, using the physical ideas assembled in step 1, write
down the basic equations you know that specify how these quantities are related to one another
mathematically. These basic relations may be in the form of Newton's laws, conservation of
energy or momentum, etc. The results of this step contain all the relevant information so you
should not need to refer to step 1 again.
3. Plan a solution: In this step you translate the physics description from step 1 and the set of
general relations in step 2 into a set of specific equations that represent the problem
mathematically. Write an outline of how you will solve these equations to see if they will yield a
solution before you go through the effort of actually doing any mathematics.
4. Execute the plan: In this step you actually solve the equations you have come up with in the
planning phase. Combine the equations as planned to get first an algebraic solution. Then plug
in all the unknown quantities, including units, to determine actual values for the desired unknown
or "target" quantities.
5. Evaluate the answer: Finally, check the answer to see that it is properly stated, reasonable,
and that you have actually answered the question asked. Tools you can use for checking
include, for instance, checking for dimensional consistency and taking special limiting cases
where you know the solution. Check to be sure the algebraic solutions don't blow up or become
imaginary for reasonable physical values of the given information.