9TH GRADE · NEWTON'S LAWS
Newton's three laws
Inertial systems, resultant and interaction pairs.
The entire theory of the lesson is collected here; you can read it without an account. In interactive mode, the same theory appears as cards, followed by questions. with checking the answer and task, and progress is saved.
Basic Concepts
Newton's second law
The acceleration of a body is determined by the vector sum of forces and is inversely proportional to the mass.
First, all forces are added as vectors, then each projection of the resultant is associated with the corresponding acceleration.
Inertial reference frame
A system in which a free body remains at rest or in uniform linear motion.
A system moving uniformly relative to an inertial system is also inertial in school mechanics.
Newton's third law
Two bodies act on each other with forces equal in magnitude, opposite and applied to different bodies.
The forces of action and reaction do not balance each other because they relate to different bodies.
Physical quantities
Resultant force
The vector sum of all forces acting on a body.
Unit: newton ·
Mass
A measure of the inertia of a body in the laws of mechanics.
Unit: kilogram ·
Lesson formulas
Newton's second law
The resultant force is equal to the product of the body's mass and its acceleration.
Related formulas
The same formulas in the reference, with symbols and units.
Tasks on the topic
Statements, answer options and the walkthrough.