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

Compact Objects: An Overview

White Dwarfs

Chandrasekhar Limit: The maximum mass of a white dwarf, about 1.4 solar masses. A white dwarf of greater mass cannot support itself and will collapse.

Roche Lobe: The volume of space a star controls gravitationally within a binary system.

Neutron Stars

Angular Momentum: A measure of the tendency of a rotating body to continue rotating. Mathematically, the product of mass, velocity, and radius.

Accretion Disk: The rotating disk that forms in some situations as matter is drawn gravitationally toward a central body.

Type I Supernova: A supernova explosion caused by the collapse of a white dwarf.

Type II Supernova: A supernova explosion caused by the collapse of a massive star.

Synchrotron Radiation: Radiation emitted... Continue reading "Compact Objects: White Dwarfs, Neutron Stars, and Black Holes" »

Chapter 6

1) How and why were the Nestors modified?

The Nestors were modified by not having the complete First Law of Robotics impressioned in them. It was modified so that the Nestors wouldn't try to save men who were working with radiation.

2) Why was the Nestor 10 lost?

Nestor 10 was lost because General Black told the robot to 'get lost.'

3) The scientist did three tests. Why are these things important?

a) Cubicles

The robots sat in the cubicles during the testing. They could not see each other, only the human in the middle of the Radiation room.

b) Heat radiation

Heat radiation was used during the last test and is harmless to robots.

c) Gamma radiation

Gamma radiation destroys robots, but small amounts are harmless to humans.

4) Did the tests succeed,

25 More Physics Questions

Interference and Diffraction

Interference: The adding together of two or more waves of the same kind that pass by the same point at the same time.

Diffraction: The ability of waves to bend around the edge of an obstacle in their path.

Rainbow Formation

Rainbows are caused by the dispersion of sunlight into its component colors when refracted by water droplets in the atmosphere.

Beta Decay and Atomic Units

Beta Decay: Occurs when there are too many neutrons. The emission of an electron by a neutron in the nucleus changes the neutron to a proton.

Atomic Mass Unit: One-twelfth of the mass of an atom of carbon-12. It is equal to approximately 1.66 x 10^-27 kg.

Electron-Volt: A unit of energy equal to the work done on an electron... Continue reading "Physics Concepts: Interference, Diffraction, and More" »

Motion in a Straight Line

V=u+at[V-T relation] (a=slope=∆x/∆ y=v-u/t)

S=ut+1/2at² [Position-T relation](displacement=area under V-T Graph=Area of rectangle+area of triangle)

v² =u² +2as[Position-velocity relation](displacement=area of trapezium=[a+b/2]h

S=v² -u² /2a

stopping distance: S=-u² /2a

Motion In a Plane

cosθ =Ax/A

sinθ =Ay/A

tanθ = Ay/Ax

| sin²θ+cos²θ=1|

magnitude of a vector; A= √Ax² +Ay²+Az² = √ Ax² +Ay²

substraction of vectors: A-B = A+(-B)

//logram law of vector addition :- [R=A+B][PN=Bcosθ][SN=Bsinθ] [R=√vb²+vc²+2VbVcCosθ

Time of flight:T=2usinθ/g→Full motion [uSinθ/g→half]

Max height: H=u²sinθ/2g

horizontal range:R=u²sin2θ/g [sin2θ =2sSnθCosθ]

Angular velocity/speed : ω(angular V) = ∆θ/∆t

linear... Continue reading "Physics: Motion, Laws, Work, Energy, Gravitation" »

Exercise 1: Correcting Sentences

The following sentences do not make sense. Correct them by replacing each word in bold with a word in bold from a different sentence. (7 x 2 = 14 points)

Write a second sentence that logically follows the first one. Pay attention to the words in bold. (3 x 3 = 9 points)

Write a suitable noun after each verb or phrase. (6 x 1 = 6 points)

Exercise 4: Completing Sentences

Complete the sentences with the words below. There are more words than you need. (7 x 3 = 21 points)

Exercise 5: Rewriting Sentences in Reported Speech

Rewrite the sentences in reported speech. (6 x 2 = 12 points)

Rewrite the sentences in reported speech using the reporting verbs below. Make any necessary changes. (6 x 3 = 18 points)

Exercise 7: Completing... Continue reading "Unit 6 Level 1 Vocabulary and Grammar Exercises" »

History of Electricity

Space Exploration Vocabulary

Satellite: An artificial body placed in orbit around the Earth, Moon, or another planet to collect information or for communication.

Man-made: Caused by human beings.

Atmosphere: The envelope of gases surrounding the Earth or another planet.

Gravity: The force that attracts a body towards the center of the Earth or towards any other physical body having mass.

Space Capsule: A small spacecraft or the part of a larger one that contains the instruments or crew.

Cosmonaut: An astronaut of the Soviet or Russian space program.

Orbit (verb): To move in orbit around a star or planet.

Re-enter: To go back to a place where you were earlier or to an activity that you did or were doing earlier.

Spacecraft: A vehicle used for traveling... Continue reading "Space Exploration Vocabulary: Key Terms Defined" »

What is the Permeability of a Material and How Does it Differ from Permittivity?

Permeability (µ) measures a material's magnetic response, while permittivity (ε) measures its electric response.

Under What Condition Do Electric and Magnetic Fields Become Coupled?

Electric and magnetic fields become coupled under dynamic conditions, meaning when current, electric field, or magnetic field changes over time.

What Happens to a Waveform's Phasor When Time-Integrated?

When a waveform is time-integrated, its phasor is divided by jω.

Can Phasor Domain Equations Calculate Situations with Signals at Multiple Frequencies?

No, phasor domain equations cannot handle signals at multiple frequencies because they remove time dependence, which must be consistent... Continue reading "Electromagnetism: Key Concepts and FAQs" »

Types of Bias

Bias by omission – leaving one side out of an article, or a series of articles over a period of time; ignoring facts that tend to disprove claims of a group, or that support beliefs by a different group; bias by omission can occur either within a story, or over the long term as a particular news outlet reports one set of events, but not another. 

Bias by selection of sources – including more sources that support one view over another.  This bias can also be seen when a reporter uses such phrases as “experts believe,” “observers say,” or “most people believe.”  Experts in news stories are like expert witnesses in trials.  If you know whether the defense or the prosecution called a particular expert witness to