arXiv subjects

Alan M. Nathan

Publications and source records attributed to Alan M. Nathan.

7 recordsLinked to original sources

arXiv2016

Oblique Collisions of Baseballs and Softballs with a Bat

Experiments are done by colliding a swinging bat with a stationary baseball or softball. Each collision was recorded with high-speed cameras, from which the post-impact speed, launch angle, and spin of the ball could be determined. Initial bat speeds were in the range 63-88 mph, producing launch angles in the range 0$^\circ$-30$^\circ$ and spins in the range 0-3500 rpm. The results are analyzed in the context of a ball-bat collision model and the parameters of that model are determined. For both baseballs and softballs, the data are consistent with a mechanism whereby the ball grips the surface of the bat, stretching the ball in the transverse direction and resulting in a spin that was up to 40$\%$ greater than would be obtained by rolling contact of rigid bodies. Using a lumped parameter contact model, baseballs are shown to be less compliant tangentially than softballs. Implications of our results for batted balls in game situations are presented.

physics.pop-ph↗

arXiv2010

Corked Bats, Juiced Balls, and Humidors: The Physics of Cheating in Baseball

Three separate questions of relevance to Major League Baseball are investigated from a physics perspective. First, can a baseball be hit farther with a corked bat? Second, is there evidence that the baseball is more lively today than in earlier years? Third, can storing baseballs in a temperature- or humidity-controlled environment significantly affect home run production? Each of these questions is subjected to a physics analysis, including an experiment, an interpretation of the data, and a definitive answer. The answers to the three questions are no, no, and yes.

physics.pop-ph↗

arXiv2008

Paradoxical popups: Why are they hard to catch?

Even professional baseball players occasionally find it difficult to gracefully approach seemingly routine pop-ups. This paper describes a set of towering pop-ups with trajectories that exhibit cusps and loops near the apex. For a normal fly ball, the horizontal velocity is continuously decreasing due to drag caused by air resistance. But for pop-ups, the Magnus force (the force due to the ball spinning in a moving airflow) is larger than the drag force. In these cases the horizontal velocity decreases in the beginning, like a normal fly ball, but after the apex, the Magnus force accelerates the horizontal motion. We refer to this class of pop-ups as paradoxical because they appear to misinform the typically robust optical control strategies used by fielders and lead to systematic vacillation in running paths, especially when a trajectory terminates near the fielder. In short, some of the dancing around when infielders pursue pop-ups can be well explained as a combination of bizarre trajectories and misguidance by the normally reliable optical control strategy, rather than apparent fielder error. Former major league infielders confirm that our model agrees with their experiences.

physics.pop-ph↗

arXiv2006

The Effect of Spin on the Flight of a Baseball

New measurements are presented of the lift on a spinning baseball. The experiment utilizes a pitching machine to project the baseball horizontally; a high-speed motion capture system to measure the initial velocity and angular velocity and to track the trajectory over ~5 m of flight; and a ruler to measure the total distance traversed by the ball. Speeds in the range v=50-110 mph and spin rates (topspin or backspin)in the range omega=1500-4500 rpm were utilized, corresponding to Reynold's numbers Re=(1.1-2.4) x 10^5 and spin parameters R*omega/v=0.1-0.6. Standard least-squares fitting procedures were used to extract the initial parameters of the trajectory and to determine the lift and drag coefficients. Comparison is made with previous measurements or parametrizations of the lift and drag coefficients, and implications for the effect of spin on the flight of a long fly ball are discussed.

physics.pop-ph↗

arXiv2006

Scattering of a Baseball by a Bat

A ball can be hit faster if it is projected without spin but it can be hit farther if it is projected with backspin. Measurements are presented in this paper of the tradeoff between speed and spin for a baseball impacting a baseball bat. The results are inconsistent with a collision model in which the ball rolls off the bat and instead imply tangential compliance in the ball, the bat, or both. If the results are extrapolated to the higher speeds that are typical of the game of baseball, they suggest that a curveball can be hit with greater backspin than a fastball, but by an amount that is less than would be the case in the absence of tangential compliance.

physics.pop-ph↗

arXiv1999

Real Compton Scattering from the Proton

Real Compton Scattering on the proton in the hard scattering regime is investigated. Recent theoretical developments are reviewed. Plans for new experimental studies at Jefferson Laboratory are presented.

hep-ph↗

arXiv1998

Real Compton Scattering at High Transverse Momentum Transfer

We discuss the physics motivation for a program of Real Compton Scattering on the proton in the regime where both the incident energy and the transverse momentum transfer are large. It is shown that such a program can test which of the various hard scattering mechanisms is dominant and can allow a measurement of a new generalized form factor that is sensitive to both the flavor and spin structure of the proton. It is further shown that the measurements are experimentally feasible using existing or already planned equipment up to incident energies of 12 GeV.

hep-ph↗