Example of pendulum is inertial frame of reference or non inertial frame of reference? because if pendulum starts moving its continuously moves without changing there period of time but is changes its velocity with there motion...
closed as unclear what you're asking by Emilio Pisanty, ja72, Chris White, Waffle's Crazy Peanut, Qmechanic♦ Aug 30 '13 at 19:12
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AS much i know this is
Frame of Reference
Inertial Frame of Reference:-
Non-Inertial Frame of Reference:-
Now coming to your question:-
so weather the frame of reference is inertial or non-inertial depend's on your position to the frame of reference weather you are inside it or outside it and weather the frame of reference is moving or stationery with respect to you
Hope you got it
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If you search this site for "inertial frame" you'll find quite a few good questions and answers that go into exactly what an inertial frame is.
My own favourite way to find out if you are in an inertial frame is to surround yourself with a sphere of test particles. In an inertial frame, e.g. floating in space, the particles will stay as a sphere with you at the centre. In an accelerated frame, e.g. standing on Earth, the particles will move relative to you (i.e. fall to the ground), and in the presence of tidal forces the sphere will change shape.
If you surround the pendulum bob with a sphere of test particles they will all fall downwards relative to the bob, so the bob is not in an inertial frame.
Response to comment:
@mikhailcazi: if you are free falling towards the Earth then you are indeed in an inertial frame. This is one of the principles on which general relativity is built - the equivalence principle.
Actually the freely falling observer is in an only approximately inertial frame. If you watch the sphere of test particles closely you'll see it change shape due to tidal forces.
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The bob of a pendulum is in a non-inertial frame as it accelerates sinusoidally. An inertial frame is precisely one that is not accelerating.
A pendulum is a non-inertial frame of reference.
A pendulum is a non-inertial frame of reference because it - as you've mentioned - has different velocities at different positions, and at different periods of time. (Acceleration of a pendulum at an angle $\theta$ from the vertical is: $g\sin^2\theta$)
$P.S:$ Constant 'time period' doesn't matter. It's the value of acceleration which does.