It is well known that a straight Nambu-Goto string is an exact solution of the equations of motion when its end moves in a circular orbit. In this paper we investigate the shape of a confining relativistic string for a general motion of its end. We determine analytically the shape of the curved string to leading order in deviation from straightness, and show that it reduces to an expected non-relativistic result. We also demonstrate numerically that in realistic meson models this deviation is always small. We further find that the angular momentum and energy are the same as for the straight string, but that the curved string has a small radial momentum not present in a straight string. Our results justify the common assumption of straight strings usually made in hadron models. ͓S0556-2821͑99͒04309-X͔

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We provide a comprehensive discussion of the corrections needed to accurately measure the acceleration of gravity using a plane pendulum. A simple laboratory experiment is described in which  g was determined to four significant figures of accuracy.

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We consider possible dynamical models for a light fermion confined by a potential field. With the Dirac equation only Lorentz scalar confinement yields normalizable wavefunctions, while with the "no pair" variant of the Dirac equation only Lorentz vector confinement has normal Regge behaviour. A systematic investigation of Regge properties and phenomenological properties is carried out, including calculations of the Isgur-Wise function. We point out that the Isgur-Wise function provides a sensitive test of confinement models.In particular, the slope of the IW function at zero recoil point is found to be ξ ′ (1) ≃ −0.90 for the Dirac equation with scalar confinement, and ξ ′ (1) ≃ −1.20 for the no pair equation with vector confinement. Using heavy-light data alone we argue against scalar confinement.