# Questions tagged [inertia]

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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2answers
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### Overcoming the inertia of a body at rest

Neglecting friction and other forces (air resistance) and assuming all forces are orthogonal the gravity vector , consider a large dense sphere at rest on a perfectly flat plane which is plumb. Now ...
2answers
63 views

### Total energy of an object in motion in free space

In order to impart motion (additional motion) to an object in free space, inertia "soaks up" an given amount of energy prior to additional movement, which is related to its mass, irrespective of any ...
2answers
102 views

### Can the origin of mass or inertia depend only of the gravitational field of matter? [closed]

The gravitacional field is directly proportional to mass or inertia. It doesn't have another property or field like this, with this power. I think that when we apply a force to an object, the ...
1answer
124 views

### Inertial stresses in Reynolds number

What is meant by the inertial stress in the definition of Reynolds number? Reynolds number = Inertial stress/ viscous stress
2answers
336 views

### Why do 2 bodies of different masses reach the ground at the same time? [duplicate]

Since inertia is the quantity that resists change in motion, and is represented by mass, and if two different objects are dropped from the same height, shouldn't the heavier mass accelerate less than ...
0answers
112 views

### How do I convert cardinal axis inertias to an arbitrary axis inertia?

I've tried to reduce this problem to the most basic form. I know the equation for a spring-mass system is generally: $$F_{\mbox{applied}} = kx + m\ddot{x} \\$$ but, in my case, I have a spring ...
1answer
901 views

### Explanation of the classic jerk and pull string system [duplicate]

It is known that when we jerk the bottom string quickly, it will break; and if we pull slowly the top string will break, while the force applied is the same. My confusion is: according to Newton's ...
5answers
2k views

### Inertia on a rotating disc?

If I toss a ball upwards in a train moving with uniform velocity, the ball will land right back in my hand. This is because the ball has inertia and it continues to move forward at the speed of train ...
2answers
119 views

### Gravity vs Electricity see-saw analogy and speed of light

Does electricity exhibit anything like the following steps: 1) A ball is rolled down from left side of a very long teeter-totter or see-saw 2) The see-saw rapidly (immediately) tilts once the ball ...
3answers
126 views

### Inertia as a fundamental interaction

Why is Inertia not included as one of the fundamental interactions, yet gravity is included as one of the four known interactions, and there is an equivalence established between gravity and inertia.
1answer
166 views

### Is Newton's third law due to inertia?

Newton's third law states that each force has an equal and opposite force. If I kicked a ball, it would apply the same force on me. Is this due to the ball's inertia? To clarify, is the ball exerting ...
1answer
54 views

### Inertia over an airplane [duplicate]

When an airplane is traveling, it moves at the same speed as the earth does due to inertia, but since, the plane is not directly touching the globe, how does is the speed of the earth is associated ...
1answer
25 views

### What happens when a electrically charged object is moving away from a charge it is attracted to(read description) [closed]

When a electrically charged object that carries momentum and inertia is attracted to a electrical field and is moving away from it, does it lose momentum as it is pulled towards it, or does it circle ...
1answer
72 views

### How to stop the propagation of waves?

I am trying to understand Newtonian equivalent law of inertia for the waves. Roughly Newton's law of inertia says that an object which is in motion in space will continue to remain in motion unless an ...
2answers
534 views

### Is a heavier baseball bat better than a lighter one?

Baseball season is coming up and I would like to know which bat is best for me. I think the heaviest bat I can swing good would be the best, but my brother thinks the lightest bat would be the best so ...
3answers
137 views

### Will anyone please explain this problem using 4 fundamental forces?

If there are only four fundamental forces (gravity,e.m.,strong,weak) in the universe and all other forces can be expressed as a function of them then consider this problem. Suppose I throw a particle '...
2answers
180 views

### Inertial force in a bus [duplicate]

While i am standing in a bus that is accelerating an inertial force is acting on me in the direction opposite of acceleration (I understand that). But, what is the magnitude of that force.I thought it ...
0answers
20 views

### Can I model objects as point masses when calculating rotational inertia? [duplicate]

I have an aircraft. On it are weapons. Weapons have masses and centers of masses. The larger aircraft system has a center of mass. I wish to calculate the cumulative rotational inertia of only the ...
1answer
162 views

4answers
287 views

### What units is the moment of inertia for a point mass?

What are the units used in the integral equation for the point mass moment of inertia. Specifically what are the units of the double integral over a region R of $r^2· \rho· dA$, where $r$ stands for ...
3answers
7k views

### Why does a bowling ball roll down faster on a slope than a tennis ball, yet both hits the ground at the same time if they're dropped from the rooftop? [closed]

If a tennis ball and a bowling ball are dropped of a rooftop, they hit the ground at the same time. But if they are rolled down a slope, the bowling ball rolls faster. Why?
5answers
5k views

### How would I move if I grew by a factor of 3 in each physical dimension?

Suppose, for the sake of this thought experiment, I am structurally identical to an average human, with the only difference being that my body is scaled in all directions by factor of 3. This would ...
1answer
143 views

### Does free-fall imply that it is impossible to quantize gravity? [closed]

I will start by stating that I realise that there already exist questions on the compatibility of GR and QM (e.g. here) but my question is different. In this essay the following argument is made (pg ...
2answers
232 views

### What causes a particular object to have a tendency to go outwards in circular motion when the centripetal force is inwards to the center [duplicate]

Like a circular bead with a thread passing through it and the system being rotated . It can't be centrifugal force as it is pseudo only and has no existence when we are already in an inertial frame ...
1answer
191 views

### A Conceptual (philosophical) doubt on equivalence principle

The reference is: Elements of Newtonian Mechanics by J.M. Knudsen; Springer; page 108 to 113. My doubt is about the significance of the apparent distinction between Gravitation and Inertia. In ...
3answers
144 views

### Question on Inertia [closed]

I'm trying to get the concept right. If an object is accelerating in a straight line, with no opposing forces acting on it, will it continue to accelerate forever due to its inertia?
0answers
27 views

### Avoiding inertial affects by accelerating larger mass in 2 body system

Suppose two bodies S and L are in proximity (asteroids say). L is substantially larger than S. For simplicity, let them initially have negligible angular and linear velocity. S will begin to fall ...
2answers
436 views

### How did Newton prove the equivalence principle with pendulums?

I know pendulums may be equivalent to a free fall but I would appreciate any further explanation for it.
1answer
529 views

### Why doesn't a test charge placed in an electric field, trace out the same path as the electric field lines?

Consider for example a positive charge placed between a positive charge and a negative charge. Initially the test charge is placed closer to positive charge. Why is path followed by the test charge ...
1answer
73 views

### Is the inertia of a mass depended of his speed?

If a ball (10 kg) falls from a height of 10 km towards an (air free) planet with an acceleration of 10 m/s² then it gains every second in speed. But is the inertia of the ball getting every second a ...
2answers
228 views

### Does horizontal inertia affect the time it takes something to reach the ground?

I am new to physics. I’m confused about how an bullet shot horizontally would land at the same time with as a bullet dropped vertically (ignoring air resistance and the curvature of Earth). Having ...
1answer
74 views

### Global momentum of a closed universe [closed]

In a universe: with 2 spatial dimensions closed (that loop on itself) with local positive and negative curvature with no attraction and no repulsion with particles randomly created by pair in the ...
3answers
663 views

### Does orientation matter when calculating inertia?

Two cylinders having the same mass, radius, size, shape and angular property are both rotating. Does this two identical cylinders have the same inertia despite their orientation?