Fundamental Principles of Physics and Dynamics

Definition of Freefall

Freefall is rectilinear motion in the vertical direction with constant acceleration performed by a body when it is dropped in a vacuum.

Freefall highlights two important features:

• 1) Objects in freefall do not experience air resistance.
• 2) All objects on the surface of the Earth accelerate downward at a value of approximately 10 m/s² (more accurately 9.8 m/s²).

Energy and Uniform Circular Motion

Energy is defined as the ability to do work.

Uniform circular motion describes the motion of a body moving with a constant speed along a circular path.

Laws of Dynamics and Forces

Dynamics is the branch of physics that describes the evolution over time of a physical system in relation to the causes of state changes or motion.

• Force: Any agent capable of modifying the momentum or shape of material bodies.
• Normal Force: The force exerted by a surface on a body resting on it. This is equal in magnitude and direction, but opposite to the force exerted by the body on the surface.
• Tensile Strength (Tension): The force experienced by strings (and objects in general) when stretched by weights at the ends. This force is limited by the length of the rope.
• Friction Forces: These occur when two materials come into contact and are responsible for the resistance to movement between those surfaces.

Newton's Three Laws of Motion

The First Law: Law of Inertia

The Law of Inertia states that if an object is left undisturbed, there will be no change in its motion. If it is at rest, it will not begin to move; if it moves in a straight line at a given speed, it will stay the same without any change in velocity.

The Second Law: Law of Force

The Law of Force explains how the properties of a body vary when forces are applied. It can be seen as the definition of force. There is a physical quantity called momentum, which is the product of a body's mass and its velocity.

The Third Law: Law of Action and Reaction

The Law of Action and Reaction is simple to understand: it explains why hitting something harder is more painful. By applying a force to a body, the body applies a force of equal magnitude back on us. For example, by resting on the ground, we apply a force (our weight) to the surface, which in turn applies an equally strong force in the opposite direction (a vector) back on us.