Principle of Reciprocal Actions and Weight
This page delves deeper into the principe des actions réciproques (principle of reciprocal actions) and introduces the concept of weight as a specific application of gravitational force.
The principle of reciprocal actions, also known as Newton's Third Law, is explained in detail:
Definition: The principe des actions réciproques states that when two objects interact, they exert forces on each other that are equal in magnitude and opposite in direction.
Key characteristics of reciprocal actions are:
- They act along the same line
- They have opposite directions
- They have equal magnitudes
Highlight: The expression vectorielle de la force d'interaction gravitationnelle (vector expression of the gravitational interaction force) always shows two equal and opposite forces between interacting objects.
The page then introduces weight as a specific example of a gravitational force:
Definition: Le poids (weight) is the gravitational force exerted by a celestial body (like Earth) on an object.
Characteristics of weight:
- Direction: Vertical
- Sense: Downward (towards the center of the Earth)
- Magnitude: Calculated using the formula P = m * g, where m is the mass of the object and g is the acceleration due to gravity
Example: For an object on Earth's surface, its weight is an example of a force gravitationnelle Terre (Earth's gravitational force) acting on it.
The page concludes by reinforcing the concept that gravitational forces between objects are always paired, equal in magnitude, and opposite in direction, as illustrated by the forces F_AB and F_BA in the accompanying diagram.
Vocabulary: The unité (unit) for force, including gravitational force and weight, is the Newton (N).
