Fundamental Concepts in Physics and Mechanics

Kinematics and Motion Description

Career Path

The career is the line formed by the various points a body follows along its path.

Reference System

A reference system is a point or a set of points used to describe the motion of a body.

Vector of a Point

The vector of a point is that defined by the origin of the chosen reference system and the point P.

Instantaneous Velocity

Instantaneous velocity is the limit that the average velocity vector approaches when the time interval approaches zero.

Vector Speed

Vector speed is the limit that the average acceleration vector approaches when the time interval $\Delta t$ approaches zero.

Physical Magnitudes

Scalars

Scalars are determined by a real number and a unit.

Vectorial Magnitudes

Vectorial magnitudes are completely defined when their module, direction, and sense are expressed.

Absolute Error

Absolute Error is the absolute difference between the approximate value obtained in the measurement and the true or exact value of the measure.

Relative Error

Relative Error is the ratio of the absolute error and the true value (or accuracy) of the measure.

Types of Motion

MRU (Uniform Rectilinear Motion)

MRU is motion in which the velocity vector remains constant.

MRUA (Uniformly Accelerated Rectilinear Motion)

MRUA is motion in which an object moves along a straight path while maintaining constant acceleration.

Forces and Elasticity

Hooke's Law

Hooke's Law states that the deformation of a body is directly proportional to the applied force.

Moment of a Couple of Forces

The module of the moment of a couple of forces is the product of the applied forces by the torque arm.

The direction is perpendicular to the plane, and the sense changes according to the sense of the applied force.

Torque System

A torque system is formed by two parallel forces of equal magnitude and opposite direction applied to a rigid solid.

Newton's Laws of Motion

First Law (Inertia)

1st Law or Inertia: A body remains at rest or in uniform rectilinear motion if no net force acts on it, or if the resultant of its forces is zero.

Second Law (Dynamics)

2nd Law or Dynamics: If a net force acts on a body, this body accelerates, with the acceleration being directly proportional to the applied force and inversely proportional to the body's mass; the proportionality constant is 1.

Third Law (Action-Reaction)

3rd Law or Action-Reaction: If an object exerts a force on another body, that body exerts a force back on the first object with the same magnitude and opposite direction.

Specific Forces

• Normal Force: The force exerted by the supporting surface on a body.
• Centripetal Force: The force applied to a body to maintain a circular path.

Energy Concepts

Energy Definition

Energy is the physical magnitude that quantifies the ability of bodies to cause changes in themselves or in other bodies.

Kinetic Energy

Kinetic energy is the energy a body possesses due to its capacity to perform work by virtue of being in motion.

Potential Energy

Potential energy is the energy possessed by bodies due to their distance above the surface of the Earth (gravitational potential energy).

Electrical Concepts

Current Intensity

Intensity: Amount of charge passing through a cross-section of a conductor per unit of time.

Electrical Resistance

Electrical Resistance depends on the resistivity of the conductor, its cross-sectional area, and its unit length.

Joule Effect

Joule Effect: Electrical energy transforming into heat energy.

Electromotive Force (EMF)

Electromotive Force (EMF): The force exerted by a generator per unit charge, or equivalently, the energy it provides per unit of charge.