Joseph C. Amato

What’s Going On Here?

From earliest times humans have speculated about the nature of matter. The Greeks with their characteristic genius developed a highly systematic set of ideas about matter. They called these ideas “physics,” but physics in the modern sense of the word comes into being only in the seventeenth century.

The Introductory Calculus‐Based Physics Textbook

Each year, more than 150 000 college students across the US enroll in calculus‐based introductory physics courses. Most of these courses are taught in the traditional mode, with students sitting passively through two or more lectures per week and reporting once or twice a week to recitation classes and laboratory sessions. Students often plow through as many as 500 pages of equation‐laden text each semester and complete one or two written assignments per week. And faculty members expend considerable effort conducting the whole enterprise.

The Heisenberg Uncertainty Principle

The photoelectric effect showed that waves behave like particles. A wave with a frequency f has a minimum packet, or quantum, of energy E = hf, where h is Planck’s constant. Compton showed that when hf is comparable to the rest mass energy mc2 of an electron, the scattering of electromagnetic radiation from electrons behaves like the scattering of one compact object from another. The particle-like behavior of light seems so prominent in these cases that the quantum of light has been given the particle-like name of “photon.” Individual photons can be detected with a photomultiplier tube; such detection also suggests a degree of localization in space that is characteristic of particles rather than waves.

Turning a Common Lab Exercise into a Challenging Lab Experiment: Revisiting the Cart on an Inclined Track.

A common lab exercise in the introductory college physics course employs a low‐friction cart and associated track to study the validity of Newtons second law. Yet for college students, especially those who have already encountered a good high school physics course, the exercise must seem a little pointless. These students have already learned to accept Newtons laws without question, and any experimental data that contradict the second law would immediately alert students to an error in procedure or analysis, or, worse, reinforce the widely held opinion that simple laws are inadequate to explain the behavior of “real” systems. A better approach is to ask students to apply their understanding of Newtons laws to determine one or more unknowns inherent in the laboratory apparatus. We illustrate this approach in the experiment described below: a small amount of complexity is added to a standard experimental exercise, forcing a careful analysis of the collected data and yielding very accurate results plus a ...

Radioactivity and the Atomic Nucleus

In 1896 Henri Becquerel discovered that compounds containing uranium emit radiations that can penetrate opaque paper and even thin sheets of metal and cause photographic plates to darken. Like x-rays, these emissions ionized air and caused electroscopes to discharge, but unlike x-rays, they occurred without any external source of excitation. Becquerel’s student, Marie Curie, named this spontaneous emission of ionizing radiation “radioactivity.”

Using Elementary Mechanics to Estimate the Maximum Range of ICBMs

North Korea’s development of nuclear weapons and, more recently, intercontinental ballistic missiles (ICBMs) has added a grave threat to world order. The threat presented by these weapons depends critically on missile range, i.e., the ability to reach North America or Europe while carrying a nuclear warhead. Using the limited information available from near-vertical test flights, how do arms control experts estimate the maximum range of an ICBM? The purpose of this paper is to show, using mathematics and concepts appropriate to a first-year calculus-based mechanics class, how a missile’s range can be estimated from the (observable) altitude attained during its test flights. This topic—while grim—affords an ideal opportunity to show students how the application of basic physical principles can inform and influence public policy. For students who are already familiar with Kepler’s laws, it should be possible to present in a single class period.

Spectra and the Bohr Atom

We come now to a new aspect of atoms: the existence of discrete energy states. Niels Bohr’s idea that atoms can possess only certain well–defined amounts of energy was a major development in our understanding of atoms. In 1911 Bohr, a young Dane who had just received his Ph.D. in physics from the University in Copenhagen, came to England to visit for a year. He worked for a while in J.J. Thomson’s laboratory in Cambridge, and then in early 1912 Bohr transferred to Manchester to work with Rutherford. Inspired by Rutherford’s concept of the atomic nucleus, Bohr subsequently developed a nuclear model of the hydrogen atom that predicted the wavelengths emitted in the spectrum of atomic hydrogen. The agreement of his predictions with observations was startlingly good.

Electric Fields and Electric Forces

This chapter introduces you to the electric field — an important and useful way to describe electric forces.

Atoms, Photons, and Quantum Mechanics

Quantum mechanics was the outcome of physicists’ twenty-five year struggle to understand the behavior of matter and light at the atomic level. This struggle began in 1900 when Max Planck explained the spectrum of light from a hot body by an ad hoc assumption that atoms absorb and emit light in bundles of energy. In 1905 Einstein argued convincingly that light is itself quantized in bundles of energy and used the idea to explain the photoelectric effect (Chap. 13). Rutherford and Moseley showed (Chaps. 16 and 17) that the atom is made of discrete elements, and Bohr showed (Chap. 17) that atoms take on definite, or as we say today, quantized states of energy.

Magnetic Field and Magnetic Force

In this chapter you meet another field of force, the magnetic field. It is quite different from the electric field. Electric fields produce forces on electrical charges whether they are moving or sitting still. The magnetic field exerts a force on an electric charge only if the charge is moving. Equally strange, the strength of the exerted force depends upon the direction of the charge’s motion. Whenever you see such peculiar behavior, you know there is a magnetic field present.