- #1
Saitama
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Homework Statement
A square metal frame in the vertical plane is hinged at O at its centre as shown in the figure. A bug moves along the rod PN which is at a distance ##l## from the hinge, such that the whole frame is always stationary, even though the frame is free to rotate in the vertical plane about the hinge. Then, the motion of the bug is simple harmonic with the time period
A)##2\pi\sqrt{l/g}##
B)##2\pi\sqrt{2l/g}##
C)##2\pi\sqrt{4l/g}##
D)##2\pi\sqrt{l/(2g)}##
Homework Equations
The Attempt at a Solution
There are two forces acting on the frame, friction (f, along PN) and normal reaction due to bug (N', vertically downwards). Since the frame must not rotate, ##fl=N'(\sqrt{2}a-2l-x) \Rightarrow f=N'(\sqrt{2}a/l-2-x/l)##, where ##x## is the displacement of bug from P and ##a## is the side length of square frame.
The bug moves from P to N and the frictional force on bug is directed from N to P. Applying Newton's second law on bug, ##m\ddot{x}=-f=N'(x/l-2-\sqrt{2}a/l)##. This doesn't turn out to be SHM.
Any help is appreciated. Thanks!