Inertia is the tendency of a body to oppose changes to its state of motion. DO NOT USE THIS TAG for moment-of-inertia!

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How does a mobile phone vibrate without any external force?

How does a mobile phone vibrate without any external force? By Newton's law, any body can't move without any external force
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2answers
520 views

How does liquid in a ball affect its rotational acceleration down a ramp?

Suppose we have a shell with mass $M$ and radius $R$. If we let that roll without slipping down a ramp of angle theta to the horizontal, we can easily find the acceleration of the shell the instant ...
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Does Unruh Radiation replace the cosmic horizon radiation?

A recent paper, titled Inertia from an Asymmetric Casimir Effect, discusses the universal horizons relative to an accelerating observer (Rindler space). A figure it used to demonstrate its point ...
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10answers
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Why is centrifugal 'force' perpendicular to line of inertia

I know that centrifugal is labeled a fictitious force only arising in a rotating reference frame, but I still struggle to understand the forces at play intuitively in tethered rotating bodies. I've ...
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5answers
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Inertia in an empty universe

I was reading a recent article on Mach's Principle. In it, the author talks about inertia in an empty universe. I'll quote some lines from the article: Imagine a single body in an otherwise empty ...
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3answers
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Why is Higgs Boson given the name “The God Particle”?

Higgs Boson (messenger particle of Higgs field) accounts for inertial mass, not gravitational mass. So, how could it account for formation of universe as we know it today? I think, gravity accounts ...
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A Basic Question about Gravity, Inertia or Momentum or something along those lines

Why is it that if I'm sitting on a seat on a bus or train and its moving quite fast, I am able to throw something in the air and easily catch it? Why is it that I haven't moved 'past' the thing during ...
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2answers
522 views

Are there 'higher order moments' in physics?

This may be a rather noob question but please let me clarify: I'm struggling to understand the use of the word 'moments' w.r.t., probability distributions. It seems after some research and poking ...
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What is the present state of Mach's Principle amongst physicists? [duplicate]

Possible Duplicate: Is Mach’s Principle Wrong? I'm doing research on gravitation and inertial forces and would like to know what is the place that Mach's Principle is occupying nowadays in ...
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212 views

In a spaceship, if a vessel suddently stops will an object inside the vessel keep going?

My question is a 2 part question. First if a vessel in space is going very fast and suddently stops (maybe it is not possible but that is not the point) will things/humans inside the vessel keep ...
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2answers
413 views

Would a sneeze by a cosmonaut in a spacesuit affect his movement?

Naive question; feel free to shoot me down It is a truism that any motion in space would continue indefinitely unless it is opposed by an external force. If a cosmonaut were to sneeze within his/her ...
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961 views

Does Dark Matter interact with Higgs Field?

Dark matter does have gravitational mass as we know from its discovery. Does it have inertial mass?
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Infinite acceleration?

Why is acceleration regulated by mass? In a frictionless environment, why doesn't an object move at infinite acceleration if force is applied on it? Force causes movement, so unless there is an ...
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8answers
748 views

How would you improve braking capability on a hovercraft? [closed]

Pretty much letting my mind free-wheel. Assume a fleet of air-supported hover-craft were to replace cars/etc on the streets. Assume also that the present traffic-signals/pedestrian rules remain ...
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4answers
223 views

What is difference between Inertial mass and gravitational mass [duplicate]

I recently read that the mass we deal with in Equation $F=Ma$ is called inertial mass and the mass we deal with in $F=Mg$ is gravitational mass. Suppose I am taking a same ball in a free fall and in ...
3
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2answers
371 views

Why does inertia happen?

In this video R P Feynman relates a story where his father told him that, even though we know the word "inertia" and what it means, nobody knows why inertia happens. Is that still true?
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4answers
370 views

Electromagnetic factors affecting inertial mass of a body affect its gravitational mass or not?

We can see that when a charge sphere is at rest & we are to put it in motion with any desired velocity than we will have to apply the same force for a longer time as if it were applied to the ...
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2answers
79 views

Alcubierre drive and inertia.

What is the inertia or velocity of a vehicle upon exiting or shutting down an Alcubierre bubble? Would the vehicle maintain the velocity it had in the bubble? I'm not sure I asked the question in a ...
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2answers
772 views

Moment of inertia of a coin

I have a a coin infinitely thin, rotating along the diameter. How to derive the formula for it's moment of inertia passing through the diameter. I was suggested to use the surface density and ...
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2answers
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Equilibrium: Inertia & Applied Force

Thank you for taking the time to read this. I am lay and will understand if the question is closed. My understanding is that in a vacuum, a constant force of $n$ applied to an object of mass $m$, ...
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2answers
168 views

London into Australia in 90 minutes

Me and my friend are having a debate on whether it would be possible for a human to travel at 15,000 miles an hour from London to Australia in the matter of 90 minutes. Would a human be able to ...
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3answers
339 views

The two faces of $F = m*a$

As I have understood, $F(t)=m \cdot a(t)$ can have 2 different meanings: When applying an external force $F$ on a point mass of mass $m$, the resulting acceleration of that mass at time $t$ is ...
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1answer
125 views

Is it humanly possible to change Earth's axis?

Just what the title states with the qualification that the change must be affected without using other celestial bodies as mentioned in the Clarke/Baxter SF 'Sunstorm'. Obviously given the momentum ...
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2answers
383 views

Does trade affect Earth's rotation? [duplicate]

Every country is trading with other countries around the world, some more than others. I was wondering if there would be any change to the Earth's rotation because of the imbalance of trade between ...
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1answer
41 views

Work done or not in this case?

I have a very simple question. A motorboat directed upstream is seen to be at rest from the bank of a river. Is the engine doing any work? Is it right to say that since it is not causing any ...
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2answers
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Does inertia increase with speed?

I have heard that when the speed of the object increase, the mass of the object also increase. (Why does an object with higher speed gain more (relativistic) mass?) So inertia which is related to ...
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2answers
462 views

Instability of a thrown tennis racquet

Someone once mentioned to me that it's impossible to throw a tennis racquet (or similarly shaped object) into the air, perpendicularly to the string plane, in such a way that it won't turn. What is ...
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1answer
80 views

Gravity vs inertia

As stated according to Newton laws of gravity, every object with mass attracts all other object with a force which produces acceleration. Basically there are several forces in the universe which ...
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1answer
44 views

Does the unit of Inertia include radians? [duplicate]

The unit for angular acceleration $\alpha$ is: $$\mathrm{rad/s^2}$$ The unit for torque is $\mathrm{Nm}$: $$\mathrm{kg\ m^2/s^2}$$ And their relationship with Inertia is: $$I = \tau/\alpha$$ So ...
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1answer
201 views

Why are there some inconsistencies with the underlying principle of center of gravity and rotational inertia?

COG: The lower the center of gravity, the more stable and object is. Rotational Inertia: The farther the concentration of mass from the defined axis of rotation, the more resistance the object has to ...
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1answer
509 views

Double gyroscope: Can a spinning pencil tumble on only one axis?

Picture an object such as item 7 on this page .. http://en.wikipedia.org/wiki/List_of_moment_of_inertia_tensors Call that the x axis and z is in to the distance. See diagram below. We are in deep ...
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1answer
143 views

Pushing, inertia of a cart system

I have a cart with another cart on top which gets pulled down by another cart on the side. There is no friction. The question is: How strongly do I have to push with $F$ to keep the cart $m_1$ ...
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61 views

Researching an automobile accident.Wondering if someone can help me as I never studied physics

I am trying do some independent research on a recent auto collision where the information released doesn't seem plausible based on the pictures that I have seen of the accidents aftermath. A ...
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2answers
243 views

Force and Torque Question on an isolated system [duplicate]

If there's a rigid rod in space, and you give some external force perpendicular to the rod at one of the ends for a short time, what happens? Specifically: What dependence does the moment of inertia ...
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590 views

“Weight” of moving object in a car collision

From time to time I see safety warning about keeping loose items in your car. The last warning used a 2kg object, and claimed that if a collision occurred at $50{km\over h}$ it would have a weight ...
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75 views

Do lawn mowers still cut the grasses if they aren't attached to the ground?

A rotary lawn mower cuts the grasses by rotating it's sharp blade on it but if the grasses aren't attached to the ground will they still cut them? What forces act on this system? I know the answer is ...
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1answer
165 views

Can inertia be explained by Bremsstrahlung?

Considering that on the atomic level objects consists of densely spaced positively and negatively charged particles, does not the acceleration of those objects lead to Bremsstrahlung of those ...
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Why does a ball bounce?

If an object is acted on by equal and opposite forces then it will be in equilibrium, and it's acceleration or velocity (and so direction as well) will not be changed. So when a ball bounces, it ...
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1answer
28 views

What is the definition of inertial mass?

What is the definition of inertial mass? I can see two options, either it's the coefficient associated with the object being accelerated in Newton's 2nd Law, or it's the coefficient relating momentum ...
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71 views

Will I be able to push a small object in front of me in the outer space?

Imagine I am standing on Earth, and pushing a tennis ball away from me. The ball moves. If it is very heavy, I will move back instead of the ball. Now consider the same scenario in outer space, where ...
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1answer
90 views

Why won't this reactionless drive idea work (motor with a moving weight in space)

I know people will say it violates many laws of motion and conservation but could anyone explain why it is so? It's NOT a question about free energy. Imagine a motor in space. It has an arm (rod) ...
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Velocity of 2 balls with different masses on a moving train after the train brakes

Question This is from my textbook: There are 2 balls of the same size made of rubber and iron respectively kept on the smooth surface of a moving train. Which ball will move faster when the train ...
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Is inertia actually a property of the force rather than the mass?

I ask this because it occurred to me that the inertial property of mass only actually arises in the context of forces (such as the EM force) as a resistance to their accelerating effect. Inertia plays ...
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What determines the speed required to pull a table cloth?

I was watching this show "Street Genius" on National Geographic and the host Tim Shaw demonstrated an experiment about Inertia, What he did was, He tied one end of a table cloth to a car through a ...
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112 views

Closed-form equation for orientation and angular velocity over time

If a rigid body, rotating freely in 3d, experiences no friction or other external forces and has an initially diagonal inertia matrix $\mathbf{I}_0$ (with $I_{11}>I_{22}>I_{33}>0$) and ...
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Calculate Rotational Intertia

If a can of soup, and a can of beans (tightly packed), are set in a race down a rough hill (has friction), the soup wins, because the inside of the can (soup) is not drawing energy from the system. ...
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3answers
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Inertia and Rocket Propulsion

We were taught in school that the law of inertia indicates that an object tend to stay the way it is, so if you throw something in space it will tend to go on forever and ever. The reason an object ...
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Why is $F = mg - T$ in this case?

The situation is as follows: I am told that $F_{net} = mg - T$ in this case, but doesn't that not take into account that $T$ isn't applied to the center of mass? Newton's second law is defined for ...
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Jumping in an elevator?

I've always been under the impression that jumping in an elevator wouldn't help at all, especially after reading a snippet of physics where Einstein said that free fall was identical to zero gravity. ...