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dankaroll
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Homework Statement
Assume a rigid body with a massless rod that pivots about point O. Displacement x is measured from equilibrium position. Assuming x is small, that the weight at the end of the rod is 5N and spring constant is 400n/m, obtain the dynamical equation of the system.
Homework Equations
[tex]\sum f =ma[/tex]
f= -kx
The Attempt at a Solution
When I look at the system, I see only two forces acting on it. One of which is gravity, and one of which is the force of the spring. So I come up with
ma=-kx-mg , so
[tex]m\ddot{x}=-kx-mg[/tex]
My intuition tells me something is missing though, since the length of the rod is given. Any suggestions?