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

Molecular Motion and States of Matter

Molecules in a gas are much more widely separated compared to a liquid or a solid, meaning they interact less frequently. Consequently, gas molecules move more freely and randomly than those in a liquid.

• Solids: Particles move only slightly.
• Liquids: Particles can move past each other.
• Gases: Particles move at high speeds.

Heat vs. Temperature

Heat is a form of energy measured in Joules (SI units). It depends on the total mass and the speed of particles, representing the total "quantity of hotness" in a system.

Temperature is not energy itself, but is related to the average kinetic energy of a substance's molecules. It depends solely on particle speed and represents the "degree of hotness."

Types of Thermometers

Mercury

Electric Current (I)

In this formula, I represents the current (measured in amperes, A) and Q is the quantity of charge (measured in coulombs, C) flowing past a specific point in the circuit within a time interval t (measured in seconds).

One coulomb of charge is equivalent to the charge carried by 6.24 × 10¹⁸ electrons. Conversely, the charge carried by a single electron is equal to -1.602 × 10^-19 C.

Voltage (V)

Where V is the voltage drop (measured in volts, V) across a device, E is the amount of energy (measured in joules, J) transformed, and Q is the amount of charge (measured in coulombs, C) that passed through the device.

Energy (E)

Electric circuits are designed to transform electrical energy into other functional forms. The amount of energy

Harmonic Oscillator

In classical mechanics, a harmonic oscillator (also known as a linear oscillator or simple oscillator) is a physical system bound to a position of stable equilibrium by a restoring force proportional to the displacement from this position. A typical example of a harmonic oscillator is a mass attached to a spring. The restoring force is the elastic force F given by Hooke’s law:

F = −kx,

where x is the displacement and k is the spring constant. The motion of a body of mass m attached to the spring is governed by Newton’s second law:

[m*(d²/dt²)] * x(t) = −kx

whose general solution is:

x(t) = Acos(ωt + φ).

Here, ω = rad(k/m) is the natural oscillating frequency, A is the amplitude of the oscillation, and φ is the phase... Continue reading "Harmonic Oscillator: Definition, Applications, and Quantum Mechanics" »

If this story had been told differently, it wouldn't have mattered to anyone. The best thing about this film is the narrative. It has such an attractive and comical principle that it catches anyone. Showing the characters with insignificant details brings them closer to the ordinary mortal, so full of obsessions or supposed oddities. They and not the protagonist of the story are, in my opinion, the success of this film. Amelie is a normal character who becomes the centerpiece of a story because of her kindness. Here she appears as a modern fairy godmother, even if she replaces the magic wand with toothpaste, slippers or intentional phrases. That's why the first part of the film, where the different human stories appear, is the one I liked the... Continue reading "Amelie: A Modern Fairy Godmother and the Power of Narrative" »

Properties of Laser Light

1. Monochromaticity

Unlike discharge lamps that emit on all atomic transitions, laser emission typically corresponds to a single atomic transition of the gain medium. The spectral line width can be much smaller than the atomic transition's due to the influence of the optical cavity.

2. Coherence

Laser beams exhibit high spatial and temporal coherence.

Spatial coherence describes the regularity of the optical phase across a beam's cross-section.

Temporal coherence refers to the duration over which the beam's phase remains well-defined. The temporal coherence time (t_c) is generally the reciprocal of the spectral linewidth (ν). Consequently, the coherence length (l_c) is: l_c = ct_c = c/ν.

3. Directionality

A key characteristic... Continue reading "Properties of Laser Light: Monochromaticity, Coherence, and More" »

Converging and Diverging Lenses

Converging Lenses

As long as the object is outside of the focal point, the image is real and inverted. When the object is inside the focal point, the image becomes virtual and upright.

Diverging Lenses

The image is always virtual and is located between the object and the lens.

Einstein's Static Universe

Einstein's static model is the first relativistic cosmological model. The model is static, finite, and of spherical spatial symmetry. I use the solution of Einstein's field equations in a homogeneous and isotropic universe—Friedmann's equation—to calculate the radius of curvature of the model (also known as "Einstein's universe"). Furthermore, I show, using a Newtonian analogy, the model's best-known feature, namely,... Continue reading "Fundamental Physics: From Optics to Cosmology" »

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What is force?

A force is a push or pull that can change the shape of an object the way that it moves. It also changes Speed and direction. You can not see. When something is moving or speeding, the force is acting.

Force arrows:

You can draw an arrow, the length of it, shows the size of force and the direction shows where is coming from.

Types:

The gravitational force, is the force that attracts you to Earth. In the earth, the force of gravity in a object is called Weight.

Electrostatic:

It acts between objects that are charged. Rubbing plastics can charge them up with electricity.

Magnetic: The magnets attract materials such as iron, steel, or nickel.

Friction:

When any object slides across a surface, the force of friction tries to stop it moving.

Market Trend and Directional Indicators

1. Trend: Direction, Trend Lines, Moving Averages, and ADX (an indicator that tells you in absolute trend what the market will do). When the ADX is above 20, it is a good moment to get into the market. If it is increasing but the market is going down, the downward trend is beginning.

Observe if there is a trend in the market using the ADX. The signal of the ADX is not related to the trend direction; 20 is the refresh level. When it is above the other two indicators, it indicates the latest top in the market. This system is useful to see if a trend exists.

Understanding Momentum and Trend Strength

2. Momentum: This represents the strength of the trend. If we have a trend but we don't have momentum, we could... Continue reading "Technical Analysis Indicators and Market Trends" »

The Importance of Light

Light is an essential form of energy for life on Earth. It is electromagnetic radiation within a specific portion of the electromagnetic spectrum. The term usually refers to visible light, which is detectable by the human eye and is responsible for our sense of sight.

How Light Travels

Light travels as transverse waves, similar to ripples in a tank of water. The direction of vibration in these waves is at 90° to the direction of travel. Because light travels in straight lines, you should always use a ruler when representing a ray of light in a drawing.

Unlike sound waves, light can travel through a vacuum (empty space). It does not require a medium to propagate, though it can pass through:

• Transparent substances: Matter

Fundamental Concepts in Earth Physics

Elastic Moduli and Seismic Waves

Elastic Moduli Definitions

• Young's Modulus (Y): Describes the fractional change in length of an object when subjected to a tensile stress. The formula is: Y = (F/A) / (ΔL/L₀)
• Bulk Modulus (K): Describes how a fractional change in volume depends on the applied pressure.
• Shear Modulus (G): Describes how an angle of shear depends upon a tangential stress.

Seismic Wave Types

• P-wave (Primary Wave): Characterized by compressional and expansion motion.
• S-wave (Secondary Wave): Characterized by shear motion.

Demonstration of Radiometric Age Dating

Derivation of the Decay Equation

If the decay rate is equal to $\lambda$, the probability that a given nucleus will decay in a time interval... Continue reading "Geophysical Principles: Elasticity, Magnetism, and Radiometric Dating Formulas" »