# Tagged Questions

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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### A trio of spinning marbles

My little brother showed me this devised act in which he stuck three marbles in a triangular pattern When he spun any of those marbles, the triplet would first rotate normally, but moments later, ...
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### Why does overcoming inertia depend upon time?

When a paper over a glass is pulled suddenly, the coin over it falls to the water. But on pulling it slowly, the coin gets pulled along with the paper. Why does the coin in the former case not feel ...
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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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### Angular velocity of disc from induced motion

I came across a question regarding linear momentum $L$ and it's conservation, however I tried and got confused. It reads: A $40kg$ girl stands on the very edge of a rotating disc of mass $50kg$ and ...
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### Moment of inertia of the sphere [closed]

My teacher has written (I is the moment of inertia of sphere) : I (about x axis) = I ( about y axis ) = I( about z axis) =I then the summation of them is equal to 3*I = 2*I(c) where c is the center ...
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### Inertia for a large mass (in outer space)

I understand that an object doesn't need a force to keep moving; that it will keep moving indefinitely in that direction at that speed. My question though is: if you were in outer space, where ...
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### Can we explain Newton's first law mathematically?

At constant speed there is no acceleration. $(f'(x)=v'=0=a)$ .If $a=0$ then $F=ma=0$ and therefore no force acts on the object so the object will continue in the same direction, if any. This is only ...
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### If a vehicle (bus, train) rapidly stops (or accelerates, or turns), why don't our hair or clothes move from the inertial force?

Many times I was sitting in a train, watching closely nearby people. If the vehicle changes it's movement rapidly (brakes, turns, etc), then obviously, people feel the inertial pseudo-force that ...
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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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### Rotating the bucket in circular motion without spilling water

In the bucket experiment when the bucket reaches the top of the circle why will it have a normal force acting on the water downwards? Doesn't normal force oppose any other force? There is no force ...
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### Why bikes are made lightweight?

From Wikipedia: The most important characteristics about a racing bicycle are its weight and stiffness. If I understand correctly, the greater the weight of the body, the greater its inertia (...
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### Does a box containing photons have more inertia than an empty box?

A box containing photons gravitates more strongly than an empty box, and thus the equivalence principle dictates that a box containing photons has more inertia than an empty box. The inescapable ...
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### Centripetal and Centrifugal force

If water stays in a pail of water that is whirled around a circular path, the water stays in the pail. But is it because of centripetal force or inertia? I'm getting confused by all the different ...
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### Moment of inertia and gravity

Would the objects have moment of Inertia if there was no gravity? Because imagine a bar, if I put my hand at the center of the bar and rotate it, it would be easier than rotate the bar picking one ...
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### What truly is mass, and is there a direct way to measure it?

We know a mass of an object of one kilogram as an object that weighs W = mg = 9.8 N and we reference it to that, (when it should as a fundamental parameter describe weight not the opposite). But if we ...
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### What is the meaning of “moment”?

What is the meaning of moment? I'm little confused about the word as there are some terms like moment of momentum, moment of mass, moment of force, etc. I want to know what exactly is meant by the ...
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### Inertial force of fluids [duplicate]

Reynold's number is the ratio of inertial force to viscous force.I also know the definition of inertial force.but where does a fluid get this force from?what are the factors responsible for this force?...
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### What is the minimal G-force curve in 2-dimensional space?

Given two parallel roads, which need to be connected, what shape of curve would produce the minimum overall horizontal G-force(s) on travelers? Is it a $sin$ or $cos$ wave? Is it a basic cubic ...
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### The principle behind Inertia and it's connection to Equilibrium

Inertia is the tendency of a force-free body to remain in that state or it is something that opposes any act of changing its equilibrium state. Mass is a measure of inertia. I have some questions ...
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### What is the relationship between potential energy and inertia?

It seems to me that the two are very similar! Potential energy seems to either explain, or partially explain, directly or indirectly, the law of inertia. I already know that bodies do not move because ...
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### Does stretching a spring with a relatively high spring constant value require more force because of its inertia?

Other than the fact that a spring has a relatively high spring constant (say 1000 N/m) and therefore requires more force per meter to stretch (not bend or twist).
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### Question about friction in rolling without slipping?

I was under the impression that for a ball/cylinder to roll without slip, there must be a static friction force that opposes the direction of motion. Why, in this case, does the friction act in the ...
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### Can you lift heavy objects in zero gravity? [closed]

I'm not someone who majored in physics and i never took the subject seriously when i was in school and im regretting that alot, there's so many things going in my mind that i cannot answer because i ...
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### Why charge is not a measure of inertia?

We know that mass is the measure of inertia of rest. Then why charge is not a measure of inertia? What causes the difference between charge and mass?
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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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### How to compensate a top-heavy platform [closed]

I have a small four-wheeled platform weighing 1.3kg with a height of 30cm. Its center-of-mass is located at 75% of the height, making it a little top-heavy. I empirically measured the angle at which ...
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### Could an asteroid land slowly on Earth's surface?

The concept in my mind is that an asteroid is on a vector similar to Earth's, but slightly slower (e.g., 50kmh slower). As Earth passes it, it enters the atmosphere at a sharp angle, and since Earth ...
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### Newton's second law of motion and viscosity [closed]

In a Coutte flow, the applied force on one of the plates can be expressed by $F = \eta A \frac{dv}{dz}$. F here can also be defined using Newton's second law of motion, $F = m \frac{dv}{dt}$. The ...
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### Does mass as a measure of inertia have a meaning in zero gravity? [duplicate]

Mass apart from the amount of material, is also a measure of the inertia of an object, ie. the resistance to change its motion. In zero gravity, does still mass count as the amount of inertia? In ...
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### Does inertia have anything to do with conservation of energy? [closed]

I have googled this and not found anything. It seems to me that if objects at rest did not resist being accelerated (which is what I once thought was the case in outside of gravity like in outer space)...
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### Why is a network pattern (weaving pattern) stronger than a whole solid surface of the same material

For example badminton racquets and huts.
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### Friction Resulting from Differing Masses

A friend and I are curious about something. We created a ramp from some wood (like a skate ramp) that's not purely circular in nature. We did so with the intent to test how the mass of an object can ...
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### Does the Inertia of a Cue Ball Affect its Reflection Angle off a Resting Billiard Ball?

Consider the following Diagram in which a Cue Ball (A) of mass M is shot twice at another pool ball with identical mass M. When the force with which the cue ball (A) is hit (v1) is increased (v2) ...
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### Reason behind Inertia

Has any physicist work on the reason behind Inertia? Why do we have inertia only during acceleration? No inertia during constant velocity.
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### Concept of mass

In classical mechanics, there seems to be a need to distinguish between inertial and gravitational mass. Some texts show how the concept of mass may be defined with some mathematical rigor. There is ...
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### When is the direction of the static friction negative?

i thought that the force of static friction exerted on an object is always going in the opposite direction of any other force exerted on the same object. however, this problem seems to disregard that ...
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### How does an Atoms electric field overcome an electrons inertia?

An electron has mass, and therefore has inertia. How does an atoms electric field perpetually overcome an electrons inertia, necessary to hold it in its shell? Does this require continual work to be ...
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### “Mass is a measure of an object’s ability to resist motion or movement of any kind”

This statement is presented as wrong, but I dont understand why. Specifically, what is the diff between motion and "movement of any kind"? Its to do with a question about inertia. I understand that ...
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### Mass, velocity and inertia [closed]

If 5 ozs of weight is my engine, and this weight starts in the back of a four wheeled vehicle traveling down a decline gaining speed due to the engine mass to allow its inertia to carry it across a ...
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### Doubts About Force and Inertia!

But then what does inertia mean at all!? Cant we calculate how much it resists the applied force? I mean considering an imaginary plane with no friction but gravity as of Earth and an enormous mass of ...
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### How to account for inertia in kinematics?

Alright, I'm only in AP Physics and I asked my teacher and he couldn't help me... I'm making a 2D physics engine and I'm having problems when it comes to gravity between objects and I think its ...
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### Understanding the inertia matrix of a tilted ellipse

I would like to control the rotation of an ellipse which is tilted by 45° with respect to the rotation axis, and I need to calculate the inertia of the load on the shaft. To be clear, on this figure I ...
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### What causes the skidding of the wheels of a moving car? Momentum or inertia?

In a moving car, when brakes are applied suddenly the wheels skid.I have these two explanations in my mind and both seems correct to me.1. The momentum of the car must be conserved so the car ...
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### Inertia on relativistic mass when particle is near speed of light

Inertia is directly proportional to mass but what happens when something travel to speed near to light. Its relativistic mass tends to infinity but that is false mass so I want to know if inertia is ...
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### How to sensor Jerk=$d^3{\bf r}/dt^3$, or higher derivatives (4th, 5th, 6th order) when applied in the equation of motion of a ballistic missile?

Given a 6th order differential equation of motion as usually used in ballastic missile dynamic models. What kind of sensors are usually used to measure Jerk, (or higher order derivatives in kinematics)...
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### How do I calculate the moment of inertia with velocity? [closed]

How do I calculate a total moment of inertia when I have point mass with velocity? It looks like this: If I understand correctly, firstly I have to find a center of mass. What do I do next?
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### How do momentum get transferred?

Simple Question , Consider two objects namely $A$ and $B$ where $B$ is stationary and $A$ is moving towards $B$ with velocity $v$. When the two objects touch each other what does actually happen ...
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### How is inertial mass different from gravitational mass? [duplicate]

I recently read that the mass we deal with in Equation $F=M_{i}a$ is called inertial mass and the mass we deal with in $F=M_{g}g$ is gravitational mass. Suppose I take a ball in a free fall and in ...