Inertia? What is it REALLY?

Question

I know that riding in a car at 50 mph with a ball in the back window has to slam on the brakes the ball will continue to travel 50mph but what exactly is IT? Does anyone have any more thoughts or explanations on this.

These are great, let me add something to it. Can rotational inertia of water be used if I have to put it back into itself?

Answer 1

In addition to the clasical answers about enertia:

The question is what is mass, and why does it have this property in the first place.

Matter is condensed energy. E=MC*C.

Electromagnetic energy such as light, heat, X-Rays, radio waves etc, are all just forms of the same thing. EM are electromagnetic waves, and waves do not have mass, but do have momentum. A wave in the ocean can knock you down, but it wasnt the water, it was the energy in the wave. The water doesnt move, but the energy carried by the wave does.
Light does not have mass, but it does have momentum, and can exert a force. When a wave moves through a medium, it has a peak, up and down, this requires the material to stretch. When a wave approaches the shore, first the water receeds(streched) and is pulled back to the ocean, before the wave arrives. It needed to suck up water to form the wave at that height.
When light moves, it also stretches the space around it to some extent, to create the peaks of the wave. This warping effect creates a momentary attractive force between all other neighboring matter and light.
When energy condenses to form matter, the energy is stored in the EM resonate wave structures. The wave energy has momentum, and is bent into resonant looping structures. Trapped in complex shaped resonate structures, it resists a change in its relative velocity due to the momentum of the EM energy. Because the speed of light is constant, any energy that is applied to the condensed energy ( matter) to change its relative velocity, will cause its mass to increase slightly.
E=MC*C.

So one way of looking at it, is that light has momentum. Light is EM energy. Matter is composed of condensed EM, which has trapped momentum. Condensed matter resists a change in motion due to the momentum of the wave energy. Condensed matter warps space, the greater the condensed EM energy, the greater the attractive warpage.

Imagine light bent into a contineous circle in space. Because of the momentum, if you try to push on the circle of light, it will resisit due to the momentum of the wave energy. The added force will cause a change in its velocity and this energy will cause the loop to increase in mass ( relatively).
Its mass must increase because c is constant.
E=m*c*c is derived from special relativity.

Austin_Semiconductor

Answer 2

Inertia is an object's ability to "resist acceleration". Acceleration being changes in its speed. Basically anything moving at a constant speed, whether that speed is zero for sitting still, or 50mph for everything in a car, it will want to stay at that speed.

Heavy things have a lot of inertia, and thus really fight against whatever is making them try to change their speed.

Compare: Pingpong ball (low inertia) vs bowling ball (high inertia).

It's easy to kick a still pingpongball and get it going. It's easy to break your foot trying to do the same to a bowling ball.

Now, what would you want in your car at 50mph when you slam on the brakes, a loose pingpong ball, or a loose bowling ball? Same idea, the pingpong ball is okay with having its speed changed by oh say your head when it flies into your head. The bowling ball would rather push your head out of the way so that it can keep flying forward.

Hope that helps. Or gives you Big Lebowski style nightmares.

Answer 3

I was never a physics whiz, but this is my explanation. The ball is still accelerating in the direction that the car was traveling in originally. The brakes were applied to the car and slowed the car down, however, the ball is not attached to the car and did not feel the effect of the brakes. So, it continues to accelerate in its original direction. Inertia, I think, at least in introductory physics courses can be regarded as mass. And the more massive an object, the more resistant it is to change. (F = ma)

Answer 4

Inertia is the tendency of any object to maintain its current direction and speed of movement. In other words, momentum.

In space, all objects move at constant speed and direction. Except, of course, planets tend to get in the way, pulling objects in via gravitational force... if you're lucky you go around the planet, if not you slam into it.

The same goes for an object that is not moving. It takes force to make it move, to accelerate it, and that is because of its inertia.

The amount of inertia (and amount of force required to accelerate an object) is dependent on its mass.

Mass is different to weight, because an object with a certain mass will have a corresponding amount of inertia, even if it's on the moon or in 'weightless' space.

i.e. a 20kg (44 lb.) object may only weigh 3kg (6 lb.) on the moon, so you could pick it up easily, but it still retains its mass of 20kg - throwing it still requires you to accelerate quite a heavy object. The only advantage is it will fly farther, since it doesn't fall as fast.

Answer 5

Newton's First Law of Motion states: Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

The car is stopping because the brakes were applied. The brakes combined with the contact of the tires with the road create the friction (external force) that stops the car. However, the ball, unless it is fastened to the rest of the car, does not encounter enough friction to slow it down. However, it does eventually stop when it strikes another object such as the back of the seat or the windshield.

Answer 6

"A body in motion tends to stay in motion. A body at rest tends to stay at rest." Newton

Inertia is a velocity given to an object that moves, and is lessoned only by an outside force.

Inertia is energy transfered from the work you do to wind up and throw a pitch to the ball which must counteract the forces of the atmosphere that it flies through.

A bat hitting a ball is a tranfer of energy... the harder you hit the ball, the more energy it will have and the farther it will go. Inertia is just energy being released in a forced direction, I think.

Answer 7

Inertia is one of Newton's laws. It states that "an object in motion will stay in motion unless acted on by a force", the object being the car with the ball in it. When the car is acted on by the force, in this case the brakes, it will slow, but the ball will stay in motion because the ball was not acted on by a force. It's like when you sprint, you tend to stay in motion unless you slow yourself.

Answer 8

Following several better definitions on Inertia combined will answer you question.

" A property of matter that causes it to resist changes in speed or direction (velocity). "
(science.nasa.gov/newhome/help/glossary.htm)

" A descriptive term for that property of a body which resists change in its motion. Two kinds of changes of motion are recognized: changes in translational motion, and changes in rotational motion. "
(www.physlink.com/Reference/Glossary.cfm)

"An object in motion will remain in motion, and an object at rest will remain at rest unless acted upon by an outside force."
(www2.newton.mec.edu/~mike_sylvia/DRAGSTERS/glossary.html)

" Is a resistance to any change in motion. In other words it is a resistance to acceleration. The more inertia an object has, then the larger the force necessary to produce a specific acceleration. Mass is associated with inertia. Larger masses have more inertia, and smaller masses have less inertia. "
(faculty.eicc.edu/tgibbons/terms.htm)

" Inertia is the tendency of any state of affairs to persist in the absence of external influences. Specifically, in physics, it is the tendency of a body to maintain its state of uniform motion unless acted on by an external force. (This is called Newton's first law of motion, taken from Galileo's principle.) The term is also used in psychology to describe a person's resistance to change. "
(en.wikipedia.org/wiki/Inertia)

Answer 9

Inertia is mass,mass of a substance is a measure of resistance to change the motion of a substance.The more the mass the more the force that is required to get it to a desired acceleration in a given time.The ball continues to move on account of its resistance to change state.

Answer 10

Physics and mathematics appear to be less inclined to use the original concept of inertia as "a tendency to maintain momentum" and instead favor the mathematically useful definition of inertia as the measure of a body's resistance to changes in momentum or simply a body's inertial mass.