# Newton's Laws of Motion – Detailed Explanation

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## Newton's Laws of Motion

Newton's Laws of Motion are three fundamental laws that describe the relationship between an object and the forces acting upon it. They were first formulated by Sir Isaac Newton in 1687 in his work "Philosophiæ Naturalis Principia Mathematica" (Mathematical Principles of Natural Philosophy).

The three laws are as follows:

1. Newton's First Law (Law of Inertia)
2. Newton's Second Law (Law of Acceleration)
3. Newton's Second Law (Law of Action-Reaction)

### Newton’s First Law :

Law of Inertia: An object at rest will remain at rest, and an object in motion will remain in motion with a constant velocity, unless acted upon by an external force.

Newton's First Law, also known as the Law of Inertia, states that an object at rest will remain at rest, and an object in motion will remain in motion with a constant velocity, unless acted upon by an external force.

In other words, an object will continue to move in a straight line at a constant speed, or remain at rest, unless a net force acts upon it. This law describes the tendency of objects to resist changes in their motion.

#### For example,

• Imagine a coin lying on a card, and the card is placed on the table. Now, place a cup over the coin and the card, so that the card and the coin are sandwiched between the table and the cup.
• According to Newton's First Law, the coin and the card will remain at rest until acted upon by an external force. In this case, the force required to move the coin and the card would have to be greater than the force of friction between the card and the table.
• So, if someone were to lift the cup, the card and the coin would remain in place until the force of friction is overcome. The force required to move the card and the coin would depend on their mass and the friction between the card and the table
Note : - The First Law is important because it provides the basis for understanding how objects behave in the absence of external forces, and how they respond to the application of forces.

### Newton’s Second Law :

Law of Acceleration: The rate of change of momentum of an object is directly proportional to the force applied, and takes place in the direction in which the force is applied.

Newton's Second Law, also known as the Law of Acceleration, states that the force applied to an object is directly proportional to its acceleration. The formula for this law is expressed as F=ma, where F is the net force applied to the object, m is the mass of the object, and a is its acceleration.

In other words, the greater the force applied to an object, the greater its acceleration will be, and the more massive an object is, the more force is required to achieve the same acceleration.

This law is important because it allows us to calculate the acceleration of an object given the force applied to it and its mass, or to determine the force required to achieve a desired acceleration. It is also used in the design of many devices, such as rockets, cars, and airplanes.

#### For example,

When the gas pedal is pressed, an unbalanced force is applied to the car, causing it to accelerate. The force applied by the engine is greater than the force of friction between the tires and the road, resulting in a net force that causes the car to accelerate forward. The greater the force applied by the engine, the greater the acceleration of the car will be.

However, if the mass of the car is increased, the same force from the engine will result in a smaller acceleration, according to Newton's second law. This is why larger, heavier cars often have larger engines to compensate for their greater mass.

### Newton’s Third Law :

Law of Action-Reaction: For every action, there is an equal and opposite reaction.

Newton's Third Law, also known as the Law of Action-Reaction, states that for every action, there is an equal and opposite reaction. This means that whenever an object exerts a force on another object, the second object exerts an equal and opposite force back on the first object.

In other words, if object A applies a force to object B, then object B applies an equal and opposite force back on object A. The forces are always equal in magnitude and opposite in direction.

This law is important because it explains why objects interact with each other and how they move. It is also important in the design of many machines, such as rockets, airplanes, and cars, where understanding the forces involved is crucial for their operation.

#### For example,

1) When two cars collide, they exert equal and opposite forces on each other. As one car hits the other, it applies a force to the second car, causing it to accelerate in the opposite direction. At the same time, the second car applies an equal and opposite force back on the first car, causing it to decelerate or come to a stop.

The force of the collision depends on the mass and velocity of the cars involved. If one car is much larger or heavier than the other, it will exert a greater force during the collision. Similarly, if one car is traveling much faster than the other, the force of the collision will be greater

2) Another example is the propulsion of a rocket. The rocket exerts a force downwards by expelling hot gases out of its engines. According to Newton's Third Law, the gases exert an equal and opposite force upwards on the rocket, propelling it upwards into space.

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