Which describes inertia

The principle of inertia is one of the fundamental principles of classical physics which are used to describe the motion of matter and how it is affected by applied forces. The vis insita, or innate force of matter is a power of resisting, by which every body, as much as in it lies, endeavors to preserve in its present state, whether it be of rest, or of moving uniformly forward in a right line. In common usage, however, people may also use the term "inertia" to refer to an object's "amount of resistance to change in velocity" which is quantified by its mass , and sometimes its momentum , depending on context e.

The term "inertia" is more properly understood as a shorthand for "the principle of inertia as described by Newton in Newton's First Law of Motion which, expressed simply, says: "An object that is not subject to any outside forces moves at a constant velocity, covering equal distances in equal times along a straight-line path. This is what misled classical theorists such as Aristotle who believed objects moved only so long as force was being applied to them.

Prior to the Renaissance in the 15th century, the generally accepted theory of motion in Western philosophy was that proposed by Aristotle around BC to BC , which stated that in the absence of an external motive power, all objects on earth would naturally come to rest in a state of no movement, and that moving objects only continue to move so long as there is a power inducing them to do so.

Aristotle explained the continued motion of projectiles, which are separated from their projector, by the action of the surrounding medium which continues to move the projectile in some way. Despite its remarkable success and general acceptance, Aristotle's concept of motion was disputed on several occasions by notable philosophers over the nearly 2 millennia of its reign.

For example, Lucretius following, presumably, Epicurus clearly stated that the 'default state' of matter was motion, not stasis. Philoponus proposed that motion was not maintained by the action of the surrounding medium but by some property implanted in the object when it was set in motion.

This was not the modern concept of inertia, for there was still the need for a power to keep a body in motion. However this view did not go unchallenged in the Islamic world , where Philoponus did have several supporters. If there is no opposing force This is as true as that an ox is not a horse.

Several Muslim scientists from the medieval Islamic world wrote Arabic treatises on theories of motion. Alhacen's model of motion thus bears resemblance to the law of inertia now known as Newton's first law of motion later stated by Galileo Galilei in the 16th century. Alhacen's contemporary, the Persian scientist Ibn Sina Latinized as Avicenna , developed an elaborate theory of motion, in which he made a distinction between the inclination and force of a projectile , and concluded that motion was a result of an inclination mayl transferred to the projectile by the thrower, and that projectile motion in a vacuum would not cease.

He was the first to argue that a force applied continuously produces acceleration , which is considered "the fundamental law of classical mechanics ", [13] and vaguely foreshadows Newton's second law of motion.

In the early 16th century, al-Birjandi , in his analysis on the Earth's rotation , developed a hypothesis similar to Galileo's notion of "circular inertia", [14] which he described in the following observational test :. This point moves with the motion of the Earth and thus there will be no difference in place of fall of the two rocks. In the 14th century, Jean Buridan rejected the notion that a motion-generating property, which he named impetus , dissipated spontaneously.

Buridan's position was that a moving object would be arrested by the resistance of the air and the weight of the body which would oppose its impetus. Despite the obvious similarities to more modern ideas of inertia, Buridan saw his theory as only a modification to Aristotle's basic philosophy, maintaining many other peripatetic views, including the belief that there was still a fundamental difference between an object in motion and an object at rest. Buridan also maintained that impetus could be not only linear, but also circular in nature, causing objects such as celestial bodies to move in a circle.

Buridan's thought was followed up by his pupil Albert of Saxony and the Oxford Calculators , who performed various experiments that further undermined the classical, Aristotelian view. Their work in turn was elaborated by Nicole Oresme who pioneered the practice of demonstrating laws of motion in the form of graphs. Shortly before Galileo's theory of inertia, Giambattista Benedetti modified the growing theory of impetus to involve linear motion alone:.

Benedetti cites the motion of a rock in a sling as an example of the inherent linear motion of objects, forced into circular motion. The law of inertia states that it is the tendency of an object to resist a change in motion.

Inertia of Rest Examples Now that you know what inertia of rest is, explore several examples. If pulled quickly, a tablecloth can be removed from underneath the dishes. The dishes have the tendency to remain still as long as the friction from the movement of the tablecloth is not too great. If a stopped car is hit by a moving car from behind, the passengers inside may experience whiplash as a result of the body moving forward but the head lagging behind.

The head is experiencing inertia. A balloon in a car will appear to move when the car moves forward, but the balloon is actually attempting to stay in the place it was, it is only the car that is moving. When a car is abruptly accelerated, drivers and passengers may feel as though their bodies are moving backward. In reality, inertia is making the body want to stay in place as the car moves forward.

If an index card is placed on top of a glass with a penny on top of it, the index card can be quickly removed while the penny falls straight into the glass, as the penny is demonstrating inertia.

When pulling a Band-Aid off, it is better to pull it fast. Your skin will remain at rest due to inertia, and the force pulls the Band-Aid off. Inertia of Motion Examples Objects in motion stay in motion or want to, just like these examples. Seat belts tighten in a car when it stops quickly. Men in space find it more difficult to stop moving because of a lack of gravity acting against them.

When playing football, a player is tackled, and his head hits the ground. The impact stops his skull, but his brain continues to move and hit the inside of his skull. His brain is showing inertia. If one drove a car directly into a brick wall, the car would stop because of the force exerted upon it by the wall. The massive bricks resist the force and the hand is not hurt. Imagine a place in the cosmos far from all gravitational and frictional influences.

Suppose that you visit that place just suppose and throw a rock. The rock will. According to Newton's first law, the rock will continue in motion in the same direction at constant speed. How much net force is required to keep the object moving at this speed and in this direction? An object in motion will maintain its state of motion. The presence of an unbalanced force changes the velocity of the object. Mac and Tosh are arguing in the cafeteria. Mac says that if he flings the Jell-O with a greater speed it will have a greater inertia.

Tosh argues that inertia does not depend upon speed, but rather upon mass. Who do you agree with? Explain why. Tosh is correct. Inertia is that quantity which depends solely upon mass.

The more mass, the more inertia. Momentum is another quantity in Physics which depends on both mass and speed. Momentum will be discussed in a later unit. Supposing you were in space in a weightless environment , would it require a force to set an object in motion? Even in space objects have mass. And if they have mass, they have inertia. That is, an object in space resists changes in its state of motion. A force must be applied to set a stationary object in motion.

Newton's laws rule - everywhere! Fred spends most Sunday afternoons at rest on the sofa, watching pro football games and consuming large quantities of food. If students are struggling with a specific objective, the Check Your Understanding assessment will help identify which objective is causing the problem and direct students to the relevant content.

However, when you slide an object across a surface, the object eventually slows down and stops. As an Amazon Associate we earn from qualifying purchases.

Want to cite, share, or modify this book? This book is Creative Commons Attribution License 4. Changes were made to the original material, including updates to art, structure, and other content updates.

Skip to Content Go to accessibility page. Physics 4. My highlights. Table of contents. Chapter Review. Test Prep. Teacher Support The learning objectives in this section will help students master the following standards: 4 Science concepts.

The student knows and applies the laws governing motion in a variety of situations. The student is expected to: D calculate the effect of forces on objects, including the law of inertia, the relationship between force and acceleration, and the nature of force pairs between objects. Figure 4. Friction acting at the wheel axles and on the surface of the tires where they touch the ground provide an external force that act against the direction of motion.

The weight W and the normal force N from the ground are two more external forces acting on the system. All external forces are represented in the figure by arrows. All of the external forces acting on the system add together, but because the wagon moves at a constant velocity, all of the forces must add up to zero.

Click to view content. Gravitational force Electrostatic force Nuclear force Frictional force. Forces and Motion—Basics In this simulation, you will first explore net force by placing blue people on the left side of a tug-of-war rope and red people on the right side of the rope by clicking people and dragging them with your mouse.

The net force acts to the right because the applied external force acted to the right. The net force acts to the left because the applied external force acted to the left.

The net force acts to the right because the frictional force acts to the right. The net force acts to the left because the frictional force acts to the left. Teacher Support Use the questions in Check Your Understanding to assess whether students have mastered the learning objectives of this section.

A body at rest tends to remain at rest and a body in motion tends to remain in motion at a constant acceleration unless acted on by a net external force. A body at rest tends to remain at rest and a body in motion tends to remain in motion at a constant velocity unless acted on by a net external force.

The rate of change of momentum of a body is directly proportional to the external force applied to the body.