Newton’s Laws of Motion

First Law - The Law of Inertia

Inertia is a body’s resistance to change in motion.
Newton’s First Law states that an object at rest will stay at rest, and an object in motion will continue in motion with the same speed and direction, unless acted upon by a net external force.
This law introduces the concept of equilibrium, where all forces acting on a body cancel each other out, resulting in zero net force and therefore no change in motion.

Second Law - The Law of Acceleration

Newton’s Second Law describes the relationship between an object’s mass, its acceleration, and the amount of force it experiences.
It states that force equals mass times acceleration (F=ma).
The resulting motion of an object will always be in the same direction as the net force, and its acceleration is proportional to the net force and inversely proportional to its mass.
This law can be used to calculate forces, accelerations, and mass given various information and contexts.

Third Law - Action-Reaction Law

Newton’s Third Law states that for every action, there is an equal and opposite reaction.
Simply put, any force exerted on a body will create a force of equal magnitude but in the opposite direction on the object that exerted the first force.
This law is applied when analysing the forces acting on bodies in contact or in motion with respect to each other.

Applications of Newton’s Laws

The laws of motion are applied to solve problems involving the motion of objects under the influence of forces.
Consideration of all forces acting on an object and careful application of the laws can predict the motion of the object.
The laws are often applied in combination with other principles such as Conservation of Energy and Momentum to fully analyse a system.

Note: Calculating forces, distances or acceleration requires algebraic manipulations, and potential use of simultaneous equations. Problems under this topic involve free body diagrams and vector addition, along with the use of sin, cos and tan functions when analysing forces at angles. Trigonometric functions, Pythagoras theorem, and algebraic manipulations are some of the mathematical tools used in solving these problems.