Newton’s laws of motion | Definition, Examples, & History (2025)

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What are Newton’s laws of motion?

Newton’s laws of motion relate an object’s motion to the forces acting on it. In the first law, an object will not change its motion unless a force acts on it. In the second law,the force on an object is equal to its mass times its acceleration. In the third law, when two objects interact, they apply forces to each other of equal magnitude and opposite direction.

Why are Newton’s laws of motion important?

Newton’s laws of motion are important because they are the foundation of classical mechanics, one of the main branches of physics. Mechanics is the study of how objects move or do not move when forces act upon them.

Newton’s laws of motion, three statements describing the relations between the forces acting on a body and the motion of the body, first formulated by English physicist and mathematician Isaac Newton, which are the foundation of classical mechanics.

Newton’s first law: the law of inertia

Newton’s first law states that if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a force. In fact, in classical Newtonian mechanics, there is no important distinction between rest and uniform motion in a straight line; they may be regarded as the same state of motion seen by different observers, one moving at the same velocity as the particle and the other moving at constant velocity with respect to the particle. This postulate is known as the law of inertia.

The law of inertia was first formulated by Galileo Galilei for horizontal motion on Earth and was later generalized by René Descartes. Although the principle of inertia is the starting point and the fundamental assumption of classical mechanics, it is less than intuitively obvious to the untrained eye. In Aristotelian mechanics and in ordinary experience, objects that are not being pushed tend to come to rest. The law of inertia was deduced by Galileo from his experiments with balls rolling down inclined planes.

For Galileo, the principle of inertia was fundamental to his central scientific task: he had to explain how is it possible that if Earth is really spinning on its axis and orbiting the Sun, we do not sense that motion. The principle of inertia helps to provide the answer: since we are in motion together with Earth and our natural tendency is to retain that motion, Earth appears to us to be at rest. Thus, the principle of inertia, far from being a statement of the obvious, was once a central issue of scientific contention. By the time Newton had sorted out all the details, it was possible to accurately account for the small deviations from this picture caused by the fact that the motion of Earth’s surface is not uniform motion in a straight line (the effects of rotational motion are discussed below). In the Newtonian formulation, the common observation that bodies that are not pushed tend to come to rest is attributed to the fact that they have unbalanced forces acting on them, such as friction and air resistance.

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Newton’s laws of motion | Definition, Examples, & History? ›

What are Newton's laws of motion? Newton's laws of motion relate an object's motion to the forces acting on it. In the first law, an object will not change its motion unless a force acts on it. In the second law, the force on an object is equal to its mass times its acceleration.

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What are Newton's 1st, 2nd, and 3rd laws of motion with examples? ›

Newton's First Law of Motion: The law of inertia states that an object at rest will remain at rest, and an object in motion will continue moving with a constant velocity, unless acted upon by an external force. Newton's Second Law of Motion: This law relates the force acting on an object to its mass and acceleration.

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What is the definition of law of motion and examples? ›

1. : a statement in dynamics: a body at rest remains at rest and a body in motion remains in uniform motion in a straight line unless acted upon by an external force. called also Newton's first law of motion.

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What are 2 real world examples of Newton's 1st law? ›

A ball rolling down a hill will continue to roll unless friction or another force stops it. If pulled quickly, a tablecloth can be removed from underneath of dishes. The dishes have the tendency to remain still as long as the friction from the movement of the tablecloth is not too great. Shaking a bottle of ketchup.

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What is Newton's 1st law? ›

The idea that objects only change their velocity due to a force is encapsulated in Newton's first law. Newton's first law: An object at rest remains at rest, or if in motion, remains in motion at a constant velocity unless acted on by a net external force.

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What are 5 examples of Newton's third law? ›

Some examples of Newton's third law are listed below.

Firing of a bullet: When a bullet is shot from a gun, the gun puts a force on the bullet that propels it forward. ...
A book lying on a table: The weight of the books is acting in the downward direction on the table (action). ...
During swimming, a swimmer moves ahead.

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What are 5 examples from your surroundings and give explanation based on Newton's law of motion? ›

Driving an empty cart and a cart full of bricks, pushing a car and a bicycle with the same force, laying a book on a table, moving, and shaking a tree are the five examples from everyday life used to teach Newton's laws of motion.

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What is 2 law of motion with examples? ›

Newton's Second Law of Motion says that acceleration (gaining speed) happens when a force acts on a mass (object). Riding your bicycle is a good example of this law of motion at work. Your bicycle is the mass. Your leg muscles pushing pushing on the pedals of your bicycle is the force.

What is 3 law of motion in real life examples? ›

A simple example of Newton's third law would be the relationship between the forces that allow a rowboat to move through the water. A person sitting in operating a rowboat would exert a force in the water using a paddle, pushing the water backward; this would be the action force.

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What is an example of the law of motion 1? ›

If you are on a train and the train is moving at a constant speed, a toy tossed into the air will go straight up and then come down. This is because the toy has inertia like the train and you. If you jump from a car or bus that is moving, your body is still moving in the direction of the vehicle.

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What does Newton's 2nd law say? ›

Newton's second law states that the acceleration of an object is directly related to the net force and inversely related to its mass. Acceleration of an object depends on two things, force and mass.

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What is Newton's third law of motion? ›

What is Newton's Third Law? Newton's third law simply states that for every action there is an equal and opposite reaction. So, if object A acts a force upon object B, then object B will exert an opposite yet equal force upon object A.

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What is an example of inertia in everyday life? ›

When a bus or a train starts suddenly, the passenger standing inside it falls backward: It happens because the feet of the passenger being in contact with the floor of the bus come in motion along with the bus but the upper part of the body remains at rest due to inertia of rest. Hence the passenger falls backward.

What is Newton's fourth law? ›

Newton's Law of gravitation is called Newton's fourth law. It states that every point mass attracts every other point mass by a force acting along the line intersecting both points. The force is proportional to the product of the two masses, and inversely proportional to the square of the distance between them.