What Should You Be Thinking When You Approach an Introductory Physics Problem?

During my introductory physics classes, I find myself asking my students this question a lot. I realize that the answer isn’t always evident, and created this non-exhaustive (I will add things as they come to mind or come up in class/conversation) list of how a physics problem might use words to indicate how to solve it.

To clarify, I am referring to inferences made on any provided information or results. The inferences listed may be useful in a variety of problems, but not all inferences can be associated with all problems. Therefore, it is still important to think through each problem yourself and use this tool only as a guide.

 „at rest“(initial) velocity = 0 (therefore, acceleration is also zero)
equilibrium (sum of forces = 0  and no change in energy)
static friction (as opposed to kinetic)
„rough surface“consider friction (if moving, kinetic; otherwise, static)
„smooth surface“no friction
„constant velocity“acceleration = 0 (simplifies kinematic equations)
no change in force (implied from above equation and Newton’s 2nd Law)
 „elastic“ collisionconservation of momentum and kinetic energy; use two conservation equations and simplify to solve for unknown variables
 „inelastic“ collision only momentum is conserved; the conservation equation should be sufficient (with other knowledge) to solve the problem
 „free fall“acceleration = gravity (be consistent with your use of the negative sign)
only concerns y-component (x-component added for parabolic motion)
 „at an angle“break apart vector (velocity, force, etc.) into x- and y-components using trigonometry

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