Notes, abstracts, papers, exams and problems of Physics

Fluid Pressure and its Effects

A fluid exerts pressure in all directions on a body immersed in it (P = d * h * g). The magnitude increases with depth. The pressure does not depend on the area. If h is the same, the pressure will be the same. But the force depends on the area. The force of the water at the bottom of a lake is greater than that exerted in a pool (F = P * A). The pressure exerted by a liquid also depends on its density. If the liquid in Torricelli's experiment had been any other than mercury and of lower density, the column would have increased.

Bathysphere: A spherical steel tank used for underwater observations, supported by a cable from a ship.

States of Matter

• Solid: Molecules are linked by very strong cohesion and have a definite

Unit III: Material Properties

1. Determination of the Characteristic Curve

It represents the functional relationships between the parameters characterizing a bomb. These curves show how and when a particular trip unit will act for a given time and current. A curve is represented by a band created by a minimum and a maximum value of time or current.

2. Lateral Deformation or Narrowing

It is a scale that measures how the width or space of a material is reduced due to an applied force.

3. Effort

Effort is the internal relationship of the materials when subjected to loads. It is usually expressed in intensity of force, i.e., force per unit area. The concept of effort is artificial; therefore, efforts cannot be measured experimentally. However, there... Continue reading "Understanding Material Properties: Stress, Strain, and Elasticity" »

Kinematics and Dynamics

Kinematics studies movement irrespective of its causes, while dynamics analyzes the causes of motion.

Types of Motion

Translational Motion

Occurs when all points of a body change position.

Rotational Motion

Occurs when a body rotates around a fixed axis; it moves but doesn't travel linearly.

Inertial Reference System

A system where the reference point (0) is at rest or moving at a constant velocity. Earth can be approximated as an inertial reference point, despite its rotation, as this motion is imperceptible to us.

Motion Concepts

Path

The trajectory of successive positions a moving point occupies in space.

Position Vector

A vector originating from the coordinate system's origin, ending at the mobile's current position.

Displacement

1. Scientist credited with the law of electromagnetic induction: Michael Faraday
2. Faraday's first discovery regarding electromagnetic induction: A changing current in one coil induces a current in another coil.
3. Factor influencing the induced EMF in a coil near a moving magnet: The speed at which the magnetic flux through the coil changes.
4. Physical quantity measuring the amount of magnetic field crossing a surface: Magnetic flux
5. Factor affecting magnetic flux through a surface: The angle between the surface and the magnetic field lines.
6. Phenomenon of electric current generation in a coil due to varying magnetic flux: Electromagnetic induction
7. Factor determining the induced EMF in a coil: The rate at which the magnetic flux through it changes.
8. Magnitude

Thermodynamics Essentials

Thermodynamics is the science that studies the work and heat exchange between a system and its environment.

First Law

This law states that the amount of energy in any system remains constant; it can only be transformed.

Systems

System

A system is an amount of material chosen for study.

Closed System

A closed system has no exchange of mass, only energy exchange.

Isolated System

An isolated system has no exchange of energy or mass.

Open System

An open system has energy and mass exchange between the environment and the system.

Surroundings

The surroundings are the region outside the system.

Boundary

The boundary is the surface separating the system from its surroundings.

Processes

A process is any change that a system experiences from... Continue reading "Thermodynamics Fundamentals: Systems, Processes, and Equilibrium" »

Understanding Force, Motion, and Newton's Laws

Force and Motion

Every action force is able to alter the state of movement or rest of bodies, or produce in them some deformation. A vector is a directed line segment.

Elements of the force vector:

• Point of application: The point on which force is applied.
• Magnitude: The intensity of the force.
• Direction: The line on which the force vector acts.
• Sense: Indicates which of the two possible orientations of force is adopted.

Types of Forces

Weight of a body: Gravitational traction force exerted by the Earth.

Power system: A set of forces acting on a body, equivalent to a single imaginary force.

Resultant force: The force on a body that produces the same effect as the set of all the forces acting; the vector sum... Continue reading "Force, Motion, and Newton's Laws Explained" »

Magnetic Properties

A magnetic field is the region around a magnet where its magnetic action is exerted. Within this region, ferrous materials are attracted to the magnet. Outside this region, no attraction is observed.

The magnetic field is represented by lines of force, conventionally going from the north to the south pole. Like poles repel each other, while opposite poles attract.

Magnetic flux is the number of lines of force passing through a surface within a magnetic field.

Materials that allow magnetic flux to pass through them easily are called permeable. They exhibit low resistance to this flux, a property known as reluctance. When a permeable material is placed in a uniform magnetic field, the lines of force concentrate within it, a phenomenon... Continue reading "Magnetism and Electromagnetism: Properties, Circuits, and Induction" »

Introduction to Structures

A structure is a group of elements designed to support various forces. These structures must be rugged, lightweight, and stable. The elements in most structures are bars. The bars support compression efforts when laid flat, supported at its ends. The resistance of the components of a structure depends on the mechanical properties of the materials used and the type of effort that will be subject. The main mechanical properties of materials are: mechanical strength, hardness, elasticity, plasticity, and tenacity. The major forces that can act on a material are: traction, compression, flexure, torsion, and shear. The resilience of the materials to different efforts is called by tests. The tests are standard procedures... Continue reading "Structure: Types, Properties, and Applications" »

Material Properties

Sensory Properties

Sensory properties are those that stimulate our senses, such as color and odor.

Optical Properties

Optical properties describe how a material interacts with light. Materials are classified as:

• Opaque: Do not allow light to pass through.
• Transparent: Allow light to pass through and can be seen through clearly.
• Translucent: Allow light to pass through but cannot be seen through clearly.

Thermal Properties

Thermal properties describe a material's behavior when exposed to heat. They are classified as:

• Conductive: Allow heat energy to pass through (e.g., metal).
• Insulating: Do not allow heat energy to pass through (e.g., glass fiber).

Magnetic Properties

Magnetic properties are determined by a material's behavior in an... Continue reading "Understanding Material Properties and Mechanical Stress Tests" »

Magnetic Fields

A magnetic field is the disturbance produced by a magnet in an area of space. It is manifested by the interactions that occur in that area with other magnets or moving electric currents.

Oersted's Experience and the Lorentz Force

Oersted's experience shows that electric charges at rest do not create magnetic fields, but if they are moving, then they do.

The Lorentz Force: If we introduce a moving charge into a magnetic field, it will experience a force given by the expression...

Similarities and Differences Between Electric and Magnetic Fields: An Analogy

• Both fields are generated by electric charges.
• Electric field strength and magnetic field strength depend inversely on the square of the distance to the point where we make the measurement.