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JolleJ
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[SOLVED] Physical pendulum
A physical pendulum constists of a rod (length = 0,30 m og mass = 0,80 kg). The rod rotates around its center. On this rod there is a moveable mass (mass=0,80kg).
Now the period of the pendulum is T = 0,83 s.
The problem to solve is: How far below the center of the rod is the mass placed?
[tex]T=2\pi*\sqrt{\frac{I}{m*g*a}}[/tex]
From what I have read a is the distance between the center of the rod and the center of gravity.
Also: For a rod: I = 1/12 * m * l^2, where l is the length of the rod.
And for the mass shifted from the center I think it is I = m*x^2 - where r is the shifted distance. (From Steiners equation where I0 = 0).
Moment of inertia I:
I = 1/12*0,8*0,3^2+0,8*x^2
Center of gravity a:
a = 0,80*x/1,6 = 0,5*x
Then this equation:
[tex]T=2\pi*\sqrt{\frac{I}{m*g*a}}[/tex]
is solved with respect to for T = 0,83 s. However this gives L = Ø. That is, a non existing result.
I really hope that someone can help me, and tell me what I've done wrong.
Thanks in advance.
Homework Statement
A physical pendulum constists of a rod (length = 0,30 m og mass = 0,80 kg). The rod rotates around its center. On this rod there is a moveable mass (mass=0,80kg).
Now the period of the pendulum is T = 0,83 s.
The problem to solve is: How far below the center of the rod is the mass placed?
Homework Equations
[tex]T=2\pi*\sqrt{\frac{I}{m*g*a}}[/tex]
From what I have read a is the distance between the center of the rod and the center of gravity.
Also: For a rod: I = 1/12 * m * l^2, where l is the length of the rod.
And for the mass shifted from the center I think it is I = m*x^2 - where r is the shifted distance. (From Steiners equation where I0 = 0).
The Attempt at a Solution
Moment of inertia I:
I = 1/12*0,8*0,3^2+0,8*x^2
Center of gravity a:
a = 0,80*x/1,6 = 0,5*x
Then this equation:
[tex]T=2\pi*\sqrt{\frac{I}{m*g*a}}[/tex]
is solved with respect to for T = 0,83 s. However this gives L = Ø. That is, a non existing result.
I really hope that someone can help me, and tell me what I've done wrong.
Thanks in advance.