The iPhysicsLabs column1 of the March 2012 issue of The Physics Teacher presents a neat use of a smartphone for teaching kinematics, but there is also an opportunity to teach about measuring devices; how we measure quantities is fundamental to physics.
For example, a traditional car speedometer does not directly measure speed; it senses the rotation rate of the wheels (from the induced electric potential in a coil created by a spinning magnet) and reports a linear speed. If a student understands how the device works, he or she knows to recalibrate the speedometer if the diameter of the tires is changed. The student can also correctly interpret what is happening when the car s wheels are spinning on slick ice; the speedometer will report a high speed even though the car is barely moving. The speedometer reading has to be interpreted based on understanding how it works.
Likewise,...
