Inertia Definition and 1000 Threads

Inertia is the resistance of any physical object to any change in its velocity. This includes changes to the object's speed, or direction of motion.
An aspect of this property is the tendency of objects to keep moving in a straight line at a constant speed, when no forces act upon them.
Inertia comes from the Latin word, iners, meaning idle, sluggish. Inertia is one of the primary manifestations of mass, which is a quantitative property of physical systems. Isaac Newton defined inertia as his first law in his Philosophiæ Naturalis Principia Mathematica, which states:

The vis insita, or innate force of matter, is a power of resisting by which every body, as much as in it lies, endeavours to preserve its present state, whether it be of rest or of moving uniformly forward in a straight line.
In common usage, the term "inertia" may refer to an object's "amount of resistance to change in velocity" or for simpler terms, "resistance to a change in motion" (which is quantified by its mass), or sometimes to its momentum, depending on the context. The term "inertia" is more properly understood as shorthand for "the principle of inertia" as described by Newton in his first law of motion: an object not subject to any net external force moves at a constant velocity. Thus, an object will continue moving at its current velocity until some force causes its speed or direction to change.
On the surface of the Earth, inertia is often masked by gravity and the effects of friction and air resistance, both of which tend to decrease the speed of moving objects (commonly to the point of rest). This misled the philosopher Aristotle to believe that objects would move only as long as force was applied to them.The principle of inertia is one of the fundamental principles in classical physics that are still used today to describe the motion of objects and how they are affected by the applied forces on them.

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  1. I

    Trying to understand the relationships between Forces, Mass and Inertia

    I hope i made clear what i mean and i really hope i can get my answers here Thank you very much for answering already
  2. I_Try_Math

    Analyzing torque of an automobile engine

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  3. I_Try_Math

    Finding the angular velocity of a pendulum

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  4. Math Amateur

    I A. P. French "Matter and Radiation: The Inertia of Energy"

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  5. davidortenn79

    B Why is it impossible to go faster than the speed of light?

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  6. potatoboy

    I How to find moment of inertia of an insect?

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  7. dcmf

    Compare rotational inertia of 2 paper cups in 2 diff orientations

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  8. F

    Calculating Flywheel Inertia Using Conservation of Energy Equations?

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  9. G

    I Inertia/Non-inertial frame - isotropy

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  10. Vic43

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  11. P

    I How Is Power Calculated in a Rotating System with Variable Speed?

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  12. KataruZ98

    I Inertia of body moving about two distinct parallel axes

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  13. G

    Setting Up a Mechanical/Electrical Inertia Measurement of Propellerarm

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  14. G

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  15. A

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  16. J

    Moment of inertia question for two plates welded together

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  17. M

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  18. G

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  19. G

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  20. S

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  21. P

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  22. L

    Moment of Inertia of something that rotates

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  23. L

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  24. L

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  25. H

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  26. N

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  27. Sri_Vars

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  28. S

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  29. A

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  30. Math Amateur

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  31. S

    Can every symmetric matrix be a matrix of inertia?

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  32. AF Fardin

    Moment of inertia of a double physical pendulum

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  33. L

    Moment of inertia of a uniform square plate

    I placed my Oxy coordinate system at the center of the square, the ##x##-axis pointing rightwards and the ##y##-axis pointing upwards. I divided the square into thin vertical strips, each of height ##h=2(\frac{L}{\sqrt{2}}-x)##, base ##dx## and mass ##dm=\sigma h...
  34. S

    I Explaining how the Higgs fields gives particles mass

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  35. C

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  36. V

    Moment of inertia of a disk about an axis not passing through its CoM

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  37. GopherTv

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  38. jaketodd

    B Are zero-point energy and inertia incompatible?

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  39. V

    What is the "r" in the moment of inertia?

    We solved this problem in class as follows: Net torque about the center of the pulley taking counterclockwise rotation to be positive = m1gR - m2gR = I_tot α, where I_tot is the moment of inertia of the full system. My professor said that I_tot = I + m1R^2 + m2R^2, where m1R^2 is the moment...
  40. George Keeling

    I Time derivative of the moment of inertia tensor

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  41. A

    Find the inertia of a sphere radius R with rotating axis through the center

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  42. M

    What's wrong with my solution? -- Area moment of inertia

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  43. Carlos Torres

    B Does the inertia of matter change in a black hole?

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  44. DrunkElk1601

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  45. curiousPep

    I Resolve moment of inertia at an angle

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  46. E

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    Hi There, I am wanting to calculate the amount of deflection (δ) from a simply supported Beam. My Beam is an Aluminium Tube ø30mm with a 3mm Wall Thickness. Force (F) - 500N Length (L) - 610mm Youngs Modulus (E) - 68 Gpa Moment of Inertia (I) - ? δ = F L³ ∕ 48 E I Q1: Is this the correct...
  47. SpaceThoughts

    I How to calculate gyroscopic inertia this setup?

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  48. A

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    This was the question (The line below is probably some translation of upper line in different language) For disc it was ma^2/2 For ring it was ma^2 For square lamina it was 2ma^2/3 For rods It was different Please explain Thank You🙏
  49. G

    Inertia units for a synchronous machine

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  50. Tapias5000

    How to determine the same moment of inertia in two different ways?

    My solution is now I am asked for the same result but in this form but I don't know where to start.
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