(Lecture: 10 minutes)

• F=ma
• Newton's laws valid in inertial frames
• moving train (constant velocity)

An explicit derivation of the Galilean transformation between (Newtonian) inertial frames is probably not helpful, although it is worth presenting the simple derivation that, since two such frames differ by a constant velocity, all accelerations are the same in either frame.

This lecture works well as a continuation of the wrap-up to the Inertial Frames SWBQ. The key point is that Newton's laws (as usually formulated) are only valid in inertial frames. The next step will be to find a formulation which holds in rotating frames; whether the result should be referred to as “Newton's laws” is a separate, and largely philosophical, question.