Smartphones and Newton’s first law in escalators and roller coasters

摘要

Your body is not a point particle. The nature and direction of the forces counteracting gravity influence your experience of uniform rectilinear motion—as does your own orientation in relation to the force of gravity. Sensors in smartphones or other devices can capture these forces, and help establish a connection between the personal experience of motion and the textbook description of forces acting on inanimate objects. This work focuses on authentic examples of uniform or nearly uniform rectilinear motion in escalators and roller coasters. Multiple complementary representations of the motion are presented, including photos, graphs of accelerometer, gyroscope and barometer data, mathematical expressions, free-body diagrams and video analysis, including screenshots. The paper aims to inspire teachers to use a larger repertoire with more variation in the examples illustrating uniform rectilinear motion. Analysing these relatively simple motions lays a good foundation for the interpretation of data from more complicated motions.