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Inertial Frames
Prompts
“What is an inertial frame?”
“Are we in one?”
Context
Estimated Time: 10 min, including wrap-up
This SWBQ requires familiarity with Newton's Second Law. Students should first be asked to write down some properties of inertial frames. After having a few minutes to respond, but without further discussion, students should be asked whether the classroom is an inertial frame.
- Confronts student understanding of inertial frames.
- Sets the stage for the rest of the course.
- (Newtonian) Inertial frames are precisely those in which Newton's laws are valid.
Wrap Up
- What is a noninertial frame in special relativity?
- Do the laws of physics apply in noninertial reference frames?
- What is a “law” of physics?
- Inertial frames are “not accelerating”.
- The Earth is not an inertial frame.
Discuss student answers, emphasizing that the notion of inertial frame is context dependent: The classroom works fine for the Newtonian mechanics of small objects, with gravity viewed as an external force, but is noninertial due to rotational acceleration.
