# Newton’s Law of Motion, Back to Basics

Newton’s law describes how a body’s motion is affected by forces. It also explains why it takes more force to move a heavy object than a light one.

It’s important to remember that Newton’s laws apply only to objects with a mass and acceleration. They break down if applied to very high speeds or very small objects.

## First Law

Newton’s law is a scientific theory about the way objects move. It was put forth by Sir Isaac Newton in 1687. It is one of the most important theories in physics and has been used to explain a number of phenomena, including the motion of planets.

In its most basic form, the law states that a body at rest will remain at rest and a body in motion will remain in motion at a constant velocity (speed) unless it is acted on by a net external force. This property of massive bodies to resist changes in their state of motion is sometimes called inertia.

The first law of motion is sometimes referred to as the law of inertia and is often called the law of conservation of momentum. It describes that a body will continue in the same direction at a constant speed unless it is disturbed by an outside force, such as a collision with another object or a change in gravity.

It also states that a body will accelerate at a rate that is directly proportional to its mass and inversely proportional to its acceleration. In other words, if a box slides at a steady speed with no external forces acting on it, it will slide faster as time passes.

When a large boulder is tossed into the air, it takes a lot of force for it to fall. The same holds true for a ball that is thrown or for a person that is pushed into the air.

In addition to the law of inertia, Newton also described the law of gravity. This is the principle that all matter exerts a force that pulls everything else towards its center. This force is determined by the mass of the matter and is the cause of Earth’s yearly journey around the Sun.

This law was important to Newton, who recognized that his ideas about gravity would help him understand the workings of the stars and planets that he had studied as a student. It also provided a clear explanation of the movement of our planet and of the tides that we see on Earth’s surface.

## Second Law

Newton’s law is one of the most important laws in physics. It explains how an object’s velocity changes as time passes. It also describes the acceleration of an object. It is commonly written as F=ma (force equals mass times acceleration).

In simplest terms, this law says that an object will remain at rest or move with a constant velocity unless it is acted on by an unbalanced force. An unbalanced force is any push, pull or twist that causes an object to change its velocity.

Students should already be familiar with the definition of acceleration, which is a change in velocity that results from a force. They can then use this information to review the first law.

The second law states that an object’s acceleration is directly proportional to the net external force acting on it and inversely proportional to its mass. This law is useful for figuring out which forces are external to a system, as discussed in the previous lesson.

This law is also used to explain how a falling object accelerates when the air resistance is negligible. In this situation, gravity acts on the falling object and causes it to accelerate toward the center of Earth.

Newton’s law is one of the most fundamental laws of physics, and its implications are still relevant today. It is an important part of how scientists and engineers study motion and create a variety of products and devices. For example, car manufacturers use this law to design crumple zones that reduce the impact of collisions on passengers.

## Third Law

Newton’s third law is a key principle that underpins the way we observe motion. It states that, for every action, there is an equal and opposite reaction. It applies to objects at rest and those accelerating, and it helps explain how we can predict the motion of some things.

Students can rely on this law to understand how forces work and how the conservation of momentum works. They can also use it to identify external forces when analyzing systems.

To demonstrate this law, students can build a simple device called a Newton’s Cradle.

The cradle has two springs that stretch and contract. A ball attached to one spring pushes on the other, and the force of the ball causes the cradle to move upward.

When students apply this law to a system, they can determine which forces are internal and which are external to the system (see Figure 4.10).

They can also use this law to calculate the acceleration of an object. They can do this by calculating the force that the object exerts on itself and then multiplying it by its mass.

If they calculate this value for a mass of 10 kg, they can estimate the acceleration that will result if the object were to be thrown into a wall.

This is because the acceleration of an object depends on its mass, and the larger the mass, the less the acceleration.

The law is also important because it allows us to compare the effect of an applied force on objects of different mass. For example, if you applied a force of 10 newtons to a baseball and a truck, the baseball would accelerate more than the truck.

This law is a central part of science. It is the underlying foundation of all sciences, and is used by scientists to develop calculus and other related fields. Scientists question everything they see, and then test their theories systematically using the scientific method.

## Fourth Law

Newton’s law of motion is an important part of physics, and it is the basis for the study of many other scientific areas. The laws of motion are essential for understanding how objects move and for designing mechanical devices that can do so safely.

One of the most important applications of Newton’s law is the way it can be used to explain collisions between objects. If the forces on an object can be compared, it is possible to determine how much force is needed to cause a collision and how long it will take for the two objects to stop moving.

Another application of Newton’s law is the way that objects can change their speed and direction over time, which is called momentum. This is an important concept in mechanics, and it explains why the speed of a box increases when the weight inside is decreased, or vice versa.

A third application of the laws of motion is to understand how objects interact with each other. This can be done by examining how the forces between two objects affect their relative positions.

Similarly, the laws of motion can also be used to explain how different parts of a physical system behave differently over time, which is known as dynamical systems. A notable example of this is the three-body problem, which shows that the position and velocity of three identical double pendulums can vary dramatically over a short period of time, even if the initial conditions were very similar.

This phenomenon can be observed in many everyday situations. For example, when a package is dropped off a scale, its weight can be determined by comparing the force that it exerts on the surface of the scale with the force that the package’s weight would exert on the ground.

A similar phenomenon can be observed in collisions between two cars, which is the reason that cars are now made with crumple zones to slow them down in case of a crash. This decreases the amount of force required to bring two vehicles together, which makes them safer for both the drivers and passengers.