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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 or inertia tensor!

Inertia is the tendency of a body to oppose changes to its state of motion. DO NOT USE THIS TAG for moment of inertia or inertia tensor! In those cases use the tag instead.

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Why did we expect gravitational mass and inertial mass to be different?

I've read many times that the fact that gravitational mass is equal to inertial mass (as far as we can tell) used to be a puzzle. I believe that Einstein explained this by showing that gravity is itself just an inertial force. When I first…
user1551817
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Is there a fundamental reason why gravitational mass is the same as inertial mass?

The principle of equivalence - that, locally, you can't distinguish between a uniform gravitational field and a non-inertial frame accelerating in the sense opposite to the gravitational field - is dependent on the equality of gravitational and…
ravithekavi
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Couldn't we always redefine units so that inertial mass and gravitational mass are equal?

It is a known fact that inertial and gravitational masses are the same thing, and therefore are numerically equal. This is not an obvious thing, since there are even experiments trying to find a difference between the two kinds of masses. What I…
RenatoRenatoRenato
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Inertia Vs Momentum

At my recent lesson on kinematics, my teacher taught about inertia and momentum. This is what she said. Inertia: a characteristic of an object that resists changes to its state of motion. Momentum: The resistance of an object to a change in its…
Simon-Nail-It
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When a car accelerates relative to earth, why can't we say earth accelerates relative to car?

When a car moves away from a standstill, why do we say that the car has accelerated? Isn't it equally correct to say that the earth has accelerated in the reference frame of the car? What breaks the symmetry here? Do the forces applied to the car…
cometraza
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What causes a rotating object to rotate forever without external force—inertia, or something else?

Someone told me that it is not inertia, but I think it is inertia, because it will rotate forever. In my understanding, inertia is the constant motion of an object without external force. Am I wrong?
enbin
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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?

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?
Tim Verboomen
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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 result in me having 27x more mass than a normal…
maxathousand
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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
Arc
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How many types of inertia are there?

I was looking for types of inertia, but I am confused. My book says there are three types of inertia, namely inertia of rest, inertia of motion, and inertia of direction. But when I searched for these types in good books like Halliday, Randall,…
Shinnaaan
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Definition of mass

In high school physics, I was taught that mass was just how much "stuff" or matter there is in an object. However, now that I am learning physics again in college, I am taught that mass of an object (inertial mass) is how resistant an object is to…
baker
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Does the bias in a loaded die depend on gravity?

Suppose I bias a cubic plastic die by incorporating a lead pellet hidden just behind the '1' face, so that the probability $P_6$ of rolling a 6 is greater than the symmetric 1/6. Its exact behaviour when I throw it will be complicated, the…
RogerJBarlow
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Why does mass limit acceleration?

If a force of $10\,\mathrm{N}$ is applied to different objects of different mass in empty space, in the absence of gravity, why do lighter objects accelerate faster than heavier objects? Why does mass cause inertia?
Samyak Marathe
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What is the origin of the inertia?

Is there any explanation why it is harder to move an object with more mass than an object with lesser mass? What kind of force is opposing our force? Is it finalized currently and well known what the origin of inertia is, or not yet 100%? I read…
MSH
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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 conclusion seems to be that we can ascribe the…
Andrew Palfreyman
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