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Inertial and non inertial frame of reference

  1. May 12, 2015 #1
    When I was surfing on a group in Facebook, I found two concepts very difficult to understand by reading the discussions in comments. Those concepts are inertial and non inertial frame of reference. Please make me understand these two concepts in simple words. Please don't suggest links as I can't understand complex and new English words in a sentence. So please help me understand. :)
  2. jcsd
  3. May 12, 2015 #2
    An inertial frame of reference is a coordinate system in which the law of inertia is valid. If a coordinate system is accelerating then the law of inertia is not valid within the system and is therefore a non-inertial frame.
  4. May 12, 2015 #3
    If you are in a car and the car is traveling straight ahead at a constant speed, then you are in an inertial frame of reference. If you are holding the string from a helium balloon in your hand, the string will be vertical, and the balloon will stay where it is.

    If you are in a car, and the car is accelerating forward or traveling around a curve, then you are in an accelerating, non-inertial frame of reference. During the time that either of these accelerations is occurring, the string on the balloon will not be vertical. In the case where you are accelerating forward, the balloon will move toward the back, and in the case where you are going around a right turn, the balloon will move toward the left.

  5. May 12, 2015 #4
    What does law of inertia say ?
  6. May 12, 2015 #5
    If a body is traveling in a straight line at constant speed, it is experiencing no net external force. But why do I have to tell you this? Why can't you just Google "law of inertia" and find out for yourself? Or look in you textbook?

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