ATAR Notes: Forum
VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: bigtick on May 31, 2008, 02:23:06 pm
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The bob of a 1m long pendulum moves at sqrt(10) m/s when the pendulum makes 30 deg with the vertical. Find the magnitude of the bob's accel.
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I'm not really confident about this answer, but here it is lol
The only forces acting on the bob are gravity and tension .
If you draw a diagram in which thee bob is displaced by with the vertical, the restoring force will be ( is canceled by the tension). Hence the acceleration is .
When ,
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I dont exactly know kinematics all that well yet, but
?!
you cant integrate like that man :P
the force acting on the bob at any moment is and tension [opposite of gravity resolved into components parallel and orthogonal to the )
hence, the restoring force, as already found, is
i think....? [velocity wasnt even used...]
that seemed a bit too simple for the information provided...
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oops, my bad
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The given answer is a=11.1 m/s2.
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Wrong. The acceleration due to gravity will have a maximum value of when the arm of the pendulum is horizontal. It will be less at all other points.
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(http://img515.imageshack.us/img515/8109/bobzc7.png)
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Question is abusing meaning of pendulum. Please slap whoever wrote it.
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What is a simple pendulum?
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A simple pendulum could be understood as mass on the end of a rope/pole that is free to oscillate due to the force of gravity. In the situation they gave, the 'pendulum' is being powered, like a metronome, so to model it circular motion needs to be taken into account.
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A simple pendulum could be understood as mass on the end of a rope/pole that is free to oscillate due to the force of gravity. In the situation they gave, the 'pendulum' is being powered, like a metronome, so to model it circular motion needs to be taken into account.
Wait... in 'physics' land, neglecting air resistance and any other forces, the bob would rise to the same height due to conservation of energy, wouldn't it? So it doesn't need to be 'powered'?
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physics' land, neglecting air resistance and any other forces, the bob would rise to the same height due to conservation of energy, wouldn't it? So it doesn't need to be 'powered'?
It would in order to have the velocity that was given.
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but if you dropped the bob from a certain height (under a suitable gravitational force) wouldn't it eventually reach that velocity anyway?
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find the angle with the vertical when the bob is released.