Sir Isaac Newton gave the three core laws of motion that we popularly use today in our daily life and endeavors. We experience one or two of the laws on a daily basis without even knowing. As an engineer, technician, or engineering student, it is necessary for you to know how these laws affect and help us in our field. This is why today I will be explaining the three Newton’s laws of motion, their formula, and examples.
Let’s begin!
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What are the Three Newton’s Laws of Motion?
Sir Isaac Newton is the founder of Newton’s law of motion, which explains the relationship between physical objects and the forces that act upon them. This is what provides the basis of modern physics.
Sir Isaac Newton was an astronomer, physicist, and English mathematician. He gave three laws that are proven to be fundamental when explaining the motion of a body.
He developed the theories of gravitation when he was 23 years old in 1666. In 1686, he introduced the three laws of motion in the “Principia Mathematica Philosophiae Naturalis.”
With the development of these laws, science is revolutionized. Kepler’s laws, together with Newton’s laws, explained why planets move in elliptical orbits rather than in circles.
- First Law – An object continues to be under a state of uniform motion unless an external force acts on it.
- Second Law – The acceleration of an object depends on the mass of the object and the amount of force applied.
- Third Law – Whenever one object exerts a force on another object, the second object exerts an equal and opposite force on the first.
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Newton’s First Law of Motion (Law of Inertia)
The newton’s first law of motion states that “A body at rest or in uniform motion will continue to be at rest or uniform motion until and unless a net external force will act on it”.
This is a law of inertia, i.e., suppose a block is kept on the floor; this box will remain at rest. This box will change in position only if some external force is applied to it. The first law of Newton is known as the law of inertia.
The Newton’s first law is called the Law of Inertia because Newton highlighted the inherent property of objects and introduced the foundation of how forces can cause changes in motion. The law states that “An object continues to be under a state of uniform motion unless an external force acts on it.”
The object will continue in that state, whether at rest or in uniform motion, unless a net external force acts upon it.
The key takeaway on the Newton’s First Law of motion expose that an object will maintain a constant velocity in the absence of a net force resulting from unbalanced forces acting upon the object.
However, If the object is already in motion, it will continue to move at the same speed and direction. Also, if the object is at rest, it will remain stationary. So, Introducing an additional external force will cause the object’s velocity to change as it responds to the applied force.
Examples of Newton’s First Law of Motion
Below are the examples of Newton’s First Law of Motion:
- A book will remain at rest on a table until someone or something moves it.
- A train moving at a constant speed will continue moving in a straight line unless brakes are applied or it hits an obstacle.
- A hockey puck glides across the ice and will keep moving in a straight line until friction or another player stops it.
- A ball thrown in space will continue moving in the same direction indefinitely unless acted upon by an external force like gravity or collision.
- A pendulum will stay at rest until someone pushes it, and it will continue to swing back and forth until friction slows it down.
- A parked car will remain stationary until a force, like someone pushing or driving it, causes it to move.
- When you stop pedaling, a bicycle continues to move forward due to inertia, eventually slowing down because of friction and air resistance.
- An apple will remain hanging on a tree until a force, such as gravity or a gust of wind, causes it to fall.
- An airplane flying at a steady altitude and speed will continue its motion unless forces like wind or turbulence act on it.
- A soccer ball at rest on the ground will not move until a player kicks it.
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Newton’s Second Law of Motion (Law of Force)
The Newton’s second law of motion helps us to understand how bodies respond to external forces. It describes the relationship between the force acting on a body and the resulting acceleration.
Newton’s second law states that the acceleration of an object depends on the mass of the object and the amount of force applied. This law help us to determine how much an object will accelerate when introduced to a specific net force.
Its Equation highlights the relationship between force, mass, and acceleration, creating a quantitative framework for analyzing the dynamics of objects in motion.
Formula
F=ma
Where:
𝐹
F is the net force acting on an object (measured in newtons, N).
𝑚
m is the mass of the object (measured in kilograms, kg).
𝑎
a is the acceleration of the object (measured in meters per second squared, m/s²).
This formula shows that the acceleration of an object is directly proportional to the net force applied and inversely proportional to its mass. If you apply a greater force to an object, it will accelerate more, and if the object has a greater mass, it will accelerate less for the same amount of force.
Mathematically, Newton’s Second Law can be expressed as:
F represents the Force, m is the mass of the object, and a is the acceleration. This is to say that the acceleration of an object is directly proportional to the magnitude of the net force introduced in the same direction as the force, which is inversely proportional to the object’s mass.
Letter K is used in the second law equation to represent a proportionality constant when using the SI unit system, which is Equal to 1.
Finally, Newton’s Second Law is the fundamental principle that governs the relationship between force and acceleration in physics. This law explains how external forces impact the motion of objects based on their mass and the acceleration they experience.
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Problem solved on Newton’s second law of motion
Suppose a body of mass 10kg is having an acceleration of 5m/s2. What is the net force experienced by it?
Solution:
From the second law of motion, we know,
- F = ma
- Putting the values, we get:
- F = (10 x 5) N
- F = 50N
Therefore, the body is experiencing a net force of 50N.
Examples of Newton’s Second Law of Motion
Below are the examples of Newton’s Second Law of Motion:
- When you push an empty shopping cart, it accelerates quickly. If the cart is full of groceries, the same force will result in less acceleration.
- When pulling a heavy box across the floor, you need to apply a greater force to achieve the same acceleration as you would for a lighter box.
- A car accelerates faster when you press the gas pedal harder because more force is applied to overcome the car’s mass.
- A baseball will accelerate more than a bowling ball when thrown with the same amount of force because the baseball has less mass.
- The harder you pedal a bicycle, the faster it accelerates. The bicycle’s acceleration is proportional to the force you apply to the pedals.
- Lifting a heavier dumbbell requires more force and results in slower acceleration compared to lifting a lighter one.
- A rocket’s acceleration increases as more fuel is burned and more force is produced, overcoming the rocket’s mass and gravity.
- Pushing a stalled car requires a lot of force to get it moving, and the more massive the car, the slower it accelerates.
- When a baseball is thrown at high speed, it requires a greater force to catch and stop it, reflecting its high acceleration.
- A light tap on a soccer ball results in slow movement, but a strong kick accelerates the ball quickly across the field.
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Third Newton’s Law of Motion (Law of Action & Reaction)
Newton’s Third Law of Motion explains the relationship between forces exerted by interacting bodies. The law states that for every action, there is an equal and opposite reaction.
This means that when two bodies interact, they apply forces on each other that are equal in magnitude and opposite in direction. In other words, the third law of motion highlights the concept that forces always occur in pairs.
Newton’s Third Law of Motion has profound implications on conserving momentum. A moving object has a certain level of momentum that can be determined by the object’s mass and velocity.
This Third Law also revealed that the total momentum of an isolated system remains constant. This means that the total momentum before and after the interaction remains the same, regardless of the forces applied.
Examples of Newton’s Third Law of Motion
Below are the examples of Newton’s Third Law of Motion:
- As the rocket expels gas downwards, an equal and opposite force pushes the rocket upwards.
- When you walk, your foot pushes backward on the ground, and the ground pushes your foot forward with an equal force, allowing you to move.
- When you push water backward with your hands while swimming, the water pushes you forward, propelling you through the water.
- If you jump off a small boat onto the dock, the boat moves backward as you move forward, due to the equal and opposite forces.
- A bird pushes air down with its wings, and the air pushes the bird up, allowing it to stay in flight.
- When a gun is fired, the bullet moves forward, and the gun moves backward with equal force, resulting in recoil.
- When you push against a wall, the wall pushes back with equal force, which is why you don’t move through it.
- When you row a boat, the oars push water backward, and the water pushes the boat forward.
- In a tug-of-war, when one team pulls on the rope, the other team pulls back with equal force. The teams remain stationary if the forces are equal.
- When you throw a ball against a wall, the wall exerts an equal and opposite force, causing the ball to bounce back towards you.
Conclusion
Newton’s Three Laws of Motion are not just abstract physics concepts, they are the foundation of how everything moves in our universe. From a rocket launching into space, to a football rolling across the field, to the way your body jerks forward when a car stops suddenly, these laws explain it all.
- First Law teaches us that objects keep moving (or stay still) unless something forces them to change.
- Second Law gives us the math to predict exactly how motion changes when forces are applied.
- Third Law reminds us that every push has a pushback.
Understanding these laws doesn’t just make you smarter in science class, it opens your eyes to the hidden patterns of motion that happen every day.
FAQs About Newton’s Three Laws of Motion
Who discovered the three laws of motion?
Sir Isaac Newton formulated the laws in 1687 and published them in his work Philosophiæ Naturalis Principia Mathematica.
Why are Newton’s laws important?
They form the basic principles of classical mechanics, allowing us to understand and predict how objects move.
Can Newton’s laws be applied in space?
Yes. In fact, they work perfectly in the vacuum of space where there is little to no friction or air resistance.
Are Newton’s laws still valid today?
Yes, for most everyday situations. However, in extreme conditions like near the speed of light or at the atomic scale, Einstein’s theory of relativity and quantum mechanics are more accurate.
What is a real-life example of Newton’s Third Law?
When you jump off a small boat, the boat moves backward, your push against it causes it to push back on you.
How does Newton’s Second Law relate to acceleration?
It states that the acceleration of an object depends directly on the net force applied and inversely on its mass (F = ma).