1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Please explain inertia

  1. Nov 21, 2007 #1
    Ok, possibly a stupid question. BUT could someone please explain the process of intertia to me, preferably how it is applied into todays science. i have looked on the net, but its only making things worse:confused:
  2. jcsd
  3. Nov 21, 2007 #2

    Gib Z

    User Avatar
    Homework Helper

    Inertia is not a process, but rather a fundamental property of all masses, being that they will continue in their previous state of unaccelerated motion, unless acted on by an unbalanced force.

    Many badly written sites and textbooks ask the student multiple choice questions : "Which Object has more inertia : a), b) c) or d)."

    That is a horrible mistake, Inertia is a property, not quantifiable. It is like giving two squares with different length sides. Which square's sides are more equal? Rubbish. They are really getting Inertia confused with the related but different concept of momentum, which is another topic.
  4. Nov 21, 2007 #3

    I agree tat inertia is not a quantity. but mass and shape of an defenitely plays a role in inertia.
    Inertia is proportional to the objects mass. As the mass of the object increase, its inertia also increases. tats y u find it difficult to stop a moving object which is of more weight rather than a object of lesser weight.
  5. Nov 21, 2007 #4


    User Avatar
    Science Advisor

    Inertia is simply a fundamental principle/concept used in classical physics to describe why an object will remain in a straight line path unless acted upon by an external force. It's the term used to define this behavior.

    Just like Gib Z said, it's not quantifiable, but rather a property of an object.

    So, an object will not have "more" inertia than some other, they all just have inertia (i.e. the desire to stay in a straight line path).

    More massive objects will have more momentum (all things else being equal), which is what leads to this confusion some times. That is to say that most people relate momentum to inertia because it's more difficult to stop or alter the path of a massive object (due to its momentum) than a less massive object. Hence, it appears to them that the object has more inertia but really has more momentum.

    Here's some further reading...

  6. Nov 21, 2007 #5

    ya i agree with u but as per ur reply u mean to say that we find it difficult to stop a moving object bcos of its momentum as the value of momentum is the product of the object's mass and its velocity. But if u consider the other case where the object is in rest, u need to apply more initial force in order to move the object. Its bcos of the objects inertia.... In this case the momentum of the object is zero... as the velocity is zero. Hope u agree with this concept. if u have any other points abt this issue please do post it.
  7. Nov 22, 2007 #6
    firstly thanks for all your replies!

    i know what you mean about there being many ideas of how to define this. conflicting text/books etc.

    this has scratched at the surface anyway, an i shall look more into wikipedia. i did consider taht the first point of call, but though i'd drop in here first :)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook