- #1
GL_Black_Hole
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Homework Statement
Verify the Work-Energy Theorem W=ΔK for a bead of masd m constrained to lie on a frictionless stick rotating with angular velocity ω in a plane.
Homework Equations
W =∫ F⋅dr, K =m/2 v^2 [/B]
The Attempt at a Solution
Adopting polar coordinates the velocity is v = r' +r*Θ'. Finding the radial and tangential accelerations we may argue that since the stick is frictionless on the tangential force of the stick on the bead may do work. As the angular velocity was assumed constant this works out to just be the Coriolis force, 2mωr'. The line integral of this from the initial position, r_0, of the bead to a final r gives the work done as mr^2 *ω^2 -mr_0^2 *ω^2.
But the Kinetic energy is K= m/2 (r' ^2 +r^2 *ω^2), justified by the use of polar coordinates.
The 'non-conservation' of energy makes sense since work must be done to keep the rod spinning at a constant rate but if I take ΔK I don't recover W. Instead I get m/2 r'^2 +m/2 r^2 * ω^2 - m/2 r_0 ^2 *ω^2.
Where do I have an error?