Notes, summaries, assignments, exams, and problems for Physics

Earth, Moon, and Space: Key Concepts

1. Day and night are caused by:

   d. Earth's rotation on its axis.

2. Earth's rotation takes about:

   c. 24 hours.

3. One complete revolution of Earth around the sun takes about:

   c. one year.

4. Earth has seasons because:

   c. Earth's axis is tilted as it moves around the sun.

5. When the north end of Earth's axis is tilted toward the sun, North America will experience:

   d. more direct rays and longer days.

6. In the Southern Hemisphere, the summer solstice occurs when the sun is directly overhead at:

   b. 23.5° south latitude.

7. An equinox occurs when:

   a. neither end of Earth's axis is tilted toward nor away from the sun.

8. Because the moon rotates once for each revolution around Earth,

   c. you never see the far side of the moon.

9. The phase of the moon

Extrasolar Planets

An extrasolar planet is a planet orbiting a star other than our Sun. There are two general ways of learning about a distant object: directly, which means by obtaining images or spectra of the object, and indirectly, which means by inferring the object’s existence or properties without actually seeing it. There are two major indirect approaches to finding and studying extrasolar planets:

1. Observing the motion of a star to detect the subtle gravitational tugs
2. Observing changes to a star’s brightness that occur when one of its planets passes in front of the star as viewed from Earth.

Planets exert gravitational tugs on their star, causing the star to orbit around the system center of mass. Gravitational tugs: we can detect a... Continue reading "Discovering Extrasolar Planets: Methods and Significance" »

Introduction

White Dwarf Stellar Explosions

Novae: Recurrent Stellar Flares

The hydrogen build-up on the surface of a white dwarf can ignite into an explosive fusion reaction that blows off a shell of gas. Because so little mass is blown off during a nova, the explosion does not disrupt the binary system. Ignition of the infalling hydrogen can recur again with periods ranging from months to thousands of years.

White Dwarf Supernovae (Type Ia)

Subrahmanyan Chandrasekhar predicted that gravity will overcome the pressure of electron degeneracy if a white dwarf has a mass > 1.4 M_¤. Energetic electrons, which cause this pressure, reach the speed of light. If accretion brings the mass of a white dwarf above the Chandrasekhar limit, electron degeneracy can no... Continue reading "Stellar Endpoints: Supernovae, Neutron Stars, and Black Holes" »

Shock Waves: Formation and Mach Cone Angle

If the speed of a source relative to the medium exceeds the speed of sound in the medium, the Doppler equation no longer applies. In such a case, shock waves result. The half-angle of the Mach cone is given by:

Temperature Measurement and Thermometers

Temperature is an SI base quantity related to our sense of hot and cold. It is measured with a thermometer, which contains a working substance with a measurable property, such as length or pressure, that changes in a regular way as the substance becomes hotter or colder.

Zeroth Law of Thermodynamics: Thermal Equilibrium

When a thermometer and some other object are placed in contact with each other, they eventually reach thermal equilibrium. The reading of... Continue reading "Fundamental Concepts in Thermodynamics and Gas Behavior" »

Write your text here!Bernoulli's theorem, in fluid dynamics, relation among the pressure, velocity, and elevation in a moving fluid (liquid or gas), the compressibility and viscosity (internal friction) of which are negligible and the flow of which is steady, or laminar.

Photons and Electrons in the Double Slit Experiment

Evidence for Wave-Particle Duality

• A single electron or photon leaves the source with particle-like discreteness and creates a single discrete spot on the screen.
• The interference pattern, which occurs over time, is a wave property.

Diffraction Pattern and Heisenberg’s Uncertainty Principle

• We cannot measure the exact position of each electron or its exact momentum as it approaches the slit; there is uncertainty in both position and momentum.
• The uncertainty in each electron’s y-position is reduced to the width of the slit (since we are certain it passes through the slit). This increases its uncertainty in the momentum of the y-direction.
• The uncertainty in the momentum in the y-direction means

Understanding Electrostatics

Electrostatics is the branch of physics that studies the phenomena produced by charges that do not vary or move.

History of Electrostatics

6th century BC: The Greeks discovered the electrical properties of amber. When rubbed, it could attract light objects.

18th century: Benjamin Franklin conducted experiments with different materials and observed that rubbed materials could either attract or repel each other.

Franklin's Theory of Electricity

• There are only two types of electricity: positive and negative.
• Electricity is a sort of fluid present in all objects and it can flow from one object to another by rubbing them.
• When there's an excess of electricity, objects have positive electricity, and when there's a lack of electricity,