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

1. What is Electric Charge?

Electric Charge is a fundamental property that all objects possess.

2. True or False: Atomic Structure and Current

• a. The atom is comprised of bigger particles.
  FALSE. The atom is comprised of smaller particles.
• b. Protons have a negative charge.
  FALSE. Protons have a positive charge.
• c. Neutrons have a positive charge.
  FALSE. Neutrons do not have an electric charge.
• d. An electric current is a continuous movement of electrons from the positive pole to the negative pole.
  FALSE. An electric current is a continuous movement of electrons from the negative pole to the positive pole.

3. Why is Matter Neutral?

Matter is neutral because it does not have a net electric charge; the number of electrons is equal to the number of protons.... Continue reading "Fundamentals of Electric Charge and Circuits" »

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,

Fundamental Physics Definitions

Properties of Matter and Energy

Electrical Charge

Property of matter related to the proportion existing between protons and electrons.

Energy

Capacity bodies have to produce changes in themselves and in other bodies.

Types of Energy

• Kinetic Energy (E_k): Possessed by bodies in motion: E_k = 1/2 * m * v²
• Potential Energy (E_p): Possessed by bodies due to the position they occupy in space or the deformation they are experiencing. E_p = m * g * h
• Gravitational Potential Energy: The energy of a body at a certain height above the surface.
• Elastic Potential Energy: Energy of an elastic body when it is deformed.
• Mechanical Energy: Possessed by bodies due to the velocity they have and their position in space.
• Electrical Energy: Produced

The Five Stages of Laser Drilling

Stage 1: Surface Heating

The laser beam acts as a small circular heat source on the surface with a heat flux distribution largely determined by the beam intensity distribution. The rate of heating depends on the absorptivity of the metal surface, which is typically low for IR lasers. Pulse durations in laser drilling (ranging from milliseconds to nanoseconds) are shorter than the thermal response time of the material; therefore, a "steady-state" is never achieved, and heating is limited to a thin surface layer.

Stage 2: Surface Melting

If the intensity and time are sufficient, a thin layer on the surface becomes molten, but timescales are too short for significant thermal conduction into the material.

Stage 3: Vaporization

Given... Continue reading "Laser Drilling Process Stages and Interaction Phenomena" »

Light and Telescopes

What distinguishes the various types of light (radio, infrared, visible, etc)? How does the apparent brightness of light vary with distance?

Answer: Different wavelengths distinguish the various types of light. Apparent brightness becomes fainter if a star is farther away.

Atomic Structure and Spectra

What is the simple structure of an atom? How are continuous, emission, & absorption spectra formed?

Answer:

• Atom Structure: The nucleus contains nearly all of the atom's mass, consisting of protons and neutrons (though the original text mentioned 'photon and nucleus', the standard model involves protons and neutrons in the nucleus). Electrons are smeared out around the nucleus.
• Kirchhoff's Laws:
  • A hot, dense glowing object emits

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" »

Understanding the Resultant Vector

The result of a vector sum is known as the resultant vector (R = A + B + C). There are two primary methods to sum vectors graphically.

The Parallelogram Method

The Parallelogram Method only works for two vectors. First, you must draw both vectors from the same origin point using a proper scale. Then, using triangles, draw parallel auxiliary lines that touch the tip of each vector. By doing this, an intersection of the auxiliary lines is formed. The result of the vector sum is the resultant vector formed when the origin point and the intersection are joined together. The tip of the resultant vector is located at the intersection, and the direction is measured from the origin point.

The Tail-to-Tip Method

The Tail-

The Sun's Structure and Activity

The Solar Atmosphere: Layers and Characteristics

The Sun's atmosphere consists of three primary layers: the Photosphere, the Chromosphere, and the Corona.

Photosphere

• Part of the Sun we see: Covers the distance over which the Sun changes from transparent to opaque.
• Thin layer of gas, 300–400 km deep.
• Below this layer, the gas is denser and hotter, but light does not escape.
• Produces an absorption line spectrum.

Chromosphere

• Lies immediately above the photosphere.
• Discovered during eclipses in the 17th century.
• Approximately 2,000–3,000 km thick.
• Density is about 1/10,000 that of the photosphere.
• Produces an emission line spectrum.
• Its red color results from hydrogen (H) emission (n=3 to n=2 transition line).

Corona

• Observed

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" »

History of Electricity