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Am I right to surmise that the kinematics equations and Newton's 2nd law hold only for Inertial Frames of reference and since when we move ,...we accelerate and decelerate all the time.,,,, So for most real world situations, the "Laws" do not apply?

Happy New Year !!

Hello yee,

Your statements about Inertial Frames of Reference are true but your conclusion is not true as uniformly as you suspect. Usually when we move and accelerate, our motion and acceleration can be described in the inertial frame of referenced that we inhabit. And the kinematics equations and Newton's 2nd law would apply.

There are times that we are in a frame of reference that is accelerating and is therefore not inertial. Examples include when we are riding in a bus going around a corner. Accurately tossing an apple to a friend several rows ahead of you would be difficult.

I hope this helps,


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Steve Johnson


I would be delighted to help with questions up through the first year of college Physics. Particularly Electricity, Electronics and Newtonian Mechanics (motion, acceleration etc.). I decline questions on relativity and Atomic Physics. I also could discuss the Space Shuttle and space flight in general.


I have a BS in Physics and an MS in Electrical Engineering. I am retired now. My professional career was in Electrical Engineering with considerable time spent working with accelerometers, gyroscopes and flight dynamics (Physics related topics) while working on the Space Shuttle. I gave formal classroom lessons to technical co-workers periodically over a several year period.

BS Physics, North Dakota State University
MS Electrical Engineering, North Dakota State University

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