A smooth wire is bent into the shape of a helix with cylindrical polar coordinates ρ=R
and z=λφ, where R and λ are constants and the z axis is vertically up. Using z as your generalized
coordinate, write down the lagrangian for a bead of mass m threaded on the wire. Find the lagrange
equation and hence the bead’s vertical acceleration d2 z/dt
2 . In the limit that R goes to zero, what is
d2 z/dt
2
? Does the make sense?
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