We consider one-dimensional classical time-dependent Hamiltonian systems with quasi-periodic orbits. It is well known that such systems possess an adiabatic invariant which coincides with the action variable of the Hamiltonian formalism. We present a new proof of the adiabatic invariance of this quantity and illustrate our arguments by means of…

The wavelength of the light emitted by a light-emitting diode (LED) is intimately related to the band-gap energy of the semiconductor from which the LED is made. We experimentally estimate the band-gap energies of several types of LEDs, and compare them with the energies of the emitted light, which ranges from infrared to white. In spite of…

The collision of a ball with the end of a barbell illustrates the combined conservation laws of linear and angular momentum. This paper considers the instructive but unfamiliar case where the ball's incident direction of travel makes an acute angle with the barbell's connecting rod. The analysis uses the coefficient of restitution generalized to…

Textbooks play an important part in the instructional process. The purposes of this study were to develop an instrument to identify the characteristics of high school physics textbooks, and examine how appropriate the currently used textbooks were for teaching and learning physics. The criteria were identified and the instrument was developed with…

Demonstrates that infinitely many Lagrangians and Hamiltonians can be constructed from a given equation of motion. Points out the lack of an established criterion for making a proper selection. (Author/GA)

Described are responses of first-year college students to questions regarding acceleration. Responses regarding acceleration and possible reasons for student errors are discussed. (RH)

Explains the effect that depth of water has on the speed of Olympic-style racing canoes and kayaks. Indicates that canoes are harder to paddle in shallow water because the skin friction drag increases appreciable when the water depth decreases. (DH)

Defines frame of reference for the analysis of motion in a moving car, discussing the interaction of the car body, the seat springs, and the passenger when the car goes over a bump. Provides a related, but more advanced, problem with the motion of cars involving angular acceleration. (JM)

Use of spring-wound toy cars in kinematics experiments is described. The cars, used in place of traditional dynamics carts rolling down an inclined plane, are inexpensive, motivational, and give reproducible results. Details of acceleration experiments and suggestions for additional experiments are provided. (JN)

Describes an apparatus for demonstrating the second law of motion. Provides sample data and discusses the merits of this method over traditional methods of supplying a constant force. The method produces empirical best-fit lines which convincingly demonstrate that for a fixed mass, acceleration is proportional to force. (DDR)

Describes Bernoulli's equation and Poiseuille's equation for fluid dynamics. Discusses the application of the combined Bernoulli-Poiseuille equation in real flows, such as viscous flows under gravity and acceleration. (YP)

Discusses student difficulties in problem solving. Presents a structured approach to one-dimensional constant acceleration problems. Provides researcher's experience including an example problem, advantages of the approach, and student responses with two illustrations of problem solving. (YP)

Presents experiments that use the Mattel's Hot Wheels Top Speed toy set to show that work is a measure of energy transferred to or from a system. (JRH)

Presents three methods for obtaining experimental data related to acceleration of a simple pendulum. Two of the methods involve angular position measurements and the subsequent calculation of the acceleration while the third method involves a direct measurement of the acceleration. Compares these results with theoretical calculations and…

Describes the physics of what happens when a single vehicle rolls over on its side during the process of turning in an arc. (JRH)