Physics Fundamentals: Motion, Forces, and Newton's Laws

Fundamentals of Motion

Movement: A body is in motion when it changes its position relative to a fixed reference point.

• Mobile: The body that is moving.
• Trajectory: The path taken by the mobile from the point of departure to the point of arrival.
• Displacement: The line segment connecting the starting point to the arrival point. It represents the net change in position and does not generally coincide with the trajectory.

Velocity and Acceleration

Speed: The quotient of the distance traveled divided by the time spent. It is expressed as a unit of length divided by a unit of time.

Acceleration: The change in velocity experienced by a body per unit of time. In the SI system, acceleration is measured in meters per second squared (m/s²).

Gravity (g)

The force produced on bodies in free fall results in a constant acceleration for all objects, regardless of mass. This acceleration due to gravity is approximately 9.8 m/s².

Understanding Forces

Force is the cause that affects the resting state or motion of a body. Forces can produce acceleration or cause cracks and deformations in objects.

Vector Properties

Forces are vector quantities defined by:

• Intensity: The magnitude of the force, measured in Newtons (N).
• Direction: The line along which the force acts.
• Sense: The orientation along the direction (two opposite senses for each direction).
• Point of Application: The specific location where the force is applied.

Systems of Forces

A system of forces is the set of forces acting on a body. The individual forces are called components, and their combined effect is the resultant force.

• Same direction and intensity: The resultant is the sum of the intensities.
• Same direction and opposite sense: The resultant has the direction of the largest force, and the intensity is the difference between the intensities.

Newton's Laws of Motion

Newton's First Law

If no external force acts on a body, it will remain at rest or continue moving in a straight line at a constant velocity.

Newton's Second Law

This law quantifies force: the net force applied on a body is proportional to the acceleration the body experiences.

Newton's Third Law

Also known as the action and reaction principle, it states that if body A exerts a force on body B, body B exerts an equal and opposite force on body A.