Newton Laws of Motion – Examples, Definition, History, Formulas

In physics, Sir Isaac Newton’s Laws of Motion are fundamental principles that describe the relationship between a body and the forces acting upon it, and the body’s response to those forces. These laws of physics serve as the cornerstone for classical mechanics, guiding how objects move in everyday life. The First Law, often known as the Law of Inertia, states that an object will remain at rest or move at a constant velocity unless acted upon by an external force. The Second Law quantifies the force needed to change an object’s motion, asserting that force equals mass times acceleration (F=ma). Lastly, the Third Law famously proclaims that for every action, there is an equal and opposite reaction, highlighting the reciprocal nature of forces. Together, these laws not only help us understand the physical world but also enable us to predict and manipulate mechanical systems effectively.

What are Newton Laws of Motion?

History of Newton Laws of Motion

Isaac Newton unveiled his three laws of motion in 1687 within his groundbreaking work, “Mathematical Principles of Natural Philosophy,” commonly known as the “Principia.” These laws revolutionized the way humanity understood the physical world. Before Newton, the motion of objects was understood largely through the work of Aristotle, who believed that a force was necessary to keep an object in motion. This view persisted until the 17th century when Galileo’s experiments with motion laid the groundwork for Newton’s laws.

Newton’s formulation of his laws built upon Galileo’s ideas and additional observations from his contemporaries. The First Law challenged the Aristotelian view by introducing the concept of inertia, the Second Law provided a quantitative description of force, and the Third Law introduced the principle of interactions between bodies. These laws not only explained earthly motion but also celestial movements, offering a universal framework that has stood the test of time in physics.

Different Newton Laws of Motion

Newton’s First Law of Motion

Newton’s First Law of Motion, also known as the Law of Inertia, asserts that an object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. This law essentially means that if no net force acts on an object, it will not accelerate but will continue doing exactly what it was doing — staying still if at rest, or moving at the same velocity if in motion. This principle highlights the natural tendency of objects to resist changes in their state of motion, which was a significant departure from earlier beliefs that a force was needed to maintain motion.

Newton’s Second Law of Motion

Newton’s Second Law of Motion provides the quantitative measure of the forces acting on an object and its resulting acceleration. It is often expressed with the equation

• 𝐹 represents the total force applied
• m is the mass of the object
• a denotes acceleration produced.

This law indicates that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. The second law not only predicts the motion of an object under the influence of a force but also provides the foundation for understanding how different forces affect the motion of objects differently based on their mass.

Newton’s Third Law of Motion

Newton’s Third Law of Motion states that for every action, there is an equal and opposite reaction. This means that whenever one object exerts a force on another object, the second object exerts a force of equal magnitude but in the opposite direction on the first object. This law highlights the mutual interactions between pairs of objects and is fundamental in understanding concepts such as propulsion. For instance, a rocket launches into space by expelling gas downwards, which in turn pushes the rocket upwards with an equal and opposite force, illustrating Newton’s third law in action.

Newton Laws of Motion Formulas

Newton’s First Law of Motion Formula

Newton’s First Law does not have a specific formula, as it primarily introduces the concept of inertia. It states that an object will not change its motion unless a force acts upon it.

Newton’s Second Law of Motion Formula

The formula for Newton’s Second Law of Motion is 𝐹=𝑚𝑎. This formula expresses that the force 𝐹 acting on an object is equal to the mass 𝑚 of the object multiplied by its acceleration 𝑎. It quantifies how the velocity of an object changes when it is subjected to an external force.

Newton’s Third Law of Motion Formula

It is best described by the formula 𝐹₁=−𝐹₂​. This illustrates that the force F₁ exerted by the first object on the second is equal in magnitude and opposite in direction to the force 𝐹₂​ exerted by the second object on the first. This relationship shows that forces always occur in pairs that are equal and opposite.

Newton Laws of Motion Examples

Newton’s First Law of Motion Examples

1. A book resting on a table remains at rest until someone moves it.
2. A soccer ball kicked across a field continues to move in a straight line unless friction or another player stops it.
3. An apple hangs from a tree, staying in place until an external force, like the wind, dislodges it.
4. A puck glides on an ice rink and keeps moving until friction and air resistance slow it down.
5. A car cruising on a highway maintains its speed as long as the driver does not apply the brakes or the accelerator.

Examples of Newton’s Second Law of Motion

1. Pushing a light shopping cart feels easier than pushing a heavy one because it requires less force to achieve the same acceleration.
2. Increasing the force on a car’s accelerator causes the car to speed up more quickly.
3. A golfer uses more force to drive a ball further down the fairway.
4. A child on a swing goes higher as the pushing force increases.
5. A rocket launches into space with greater acceleration as more thrust is applied from its engines.

Examples of Newton’s Third Law of Motion

1. When you jump off a small boat into the water, the boat pushes back and moves in the opposite direction.
2. A baseball bat hits a ball, and the ball exerts an equal and opposite force back on the bat.
3. When walking, your feet push against the ground, and the ground pushes back with equal force, moving you forward.
4. A helicopter rises when the blades push air downwards, and the air pushes back upwards against the blades.
5. When firing a gun, the bullet moves forward, and the gun kicks back in the opposite direction.

FAQs

Which is Newton’s 1st Law of Motion?

Newton’s First Law of Motion states that an object at rest stays at rest and an object in motion remains in motion unless acted upon by an external force.

How Many Newton’s Laws Are There?

There are three Newton’s Laws of Motion, each describing different aspects of motion and forces acting on objects.

What Law is Kicking a Ball?

Kicking a ball demonstrates Newton’s Third Law of Motion, where the foot exerts a force on the ball, and the ball exerts an equal and opposite force on the foot.