Getting the Swing of Surface Gravity

Sports are a popular and effective way to illustrate physics principles. Baseball in particular presents a number of opportunities to motivate student interest and teach concepts. Several articles have appeared in this journal on this topic, illustrating a wide variety of areas of physics. In addition, several websites and an entire book are available. In this paper we describe a student-designed project that illustrates the relative surface gravity on the Earth, Sun and other solar-system bodies using baseball. We describe the project and its results here as an example of a simple, fun, and student-driven use of baseball to illustrate an important physics principle

A positive relationship between the abundance of ammonia oxidizing archaea and natural abundance δ15N of ecosystems

We present a significant relationship between the natural abundance isotopic composition of ecosystem pools and the abundance of a microbial gene. Natural abundance 15N of soils and soil DNA were analysed and compared with archaeal ammonia oxidizer abundance along an elevation gradient in northern Arizona and along a substrate age gradient in Hawai'i. There was a significant positive correlation between the abundance of archaeal amoA genes and natural abundance δ15N of total soil or DNA suggesting that ammonia oxidizing archaea play an important role in ecosystem N release. © 2013 Elsevier Ltd

Thermal management of LI-ION battery packs

A design for the thermal management of Lithium-ion battery packing as used in hybrid and electric vehicles has been developed. The design satisfies all thermal and physical issues relating to the battery packs used in vehicles including operating temperature range and volume, and, should increase battery cycle life, and, charge and discharge performances. Particular attention was devoted to the thermal management of batteries operating in extreme temperature conditions

Correlation between weight, squat, deadlift and rowing ergometer times in collegiate rowers.

“Correlation between weight, squat, deadlift and rowing ergometer times in collegiate rowers.” Jared McArthur, James Kyle Adair, and Ali Boolani Oklahoma City University Oklahoma City University Human Performance Lab Undergraduate Abstract Purpose; The purpose of the study is to determine a relationship between male rower’s ergometer time (ET) body weight (WT), height (HT), maximal Squat (SQ), and Dead Lift (DL) results. Methodology; Subjects (N=16; HT= 185.34cm ±7.19; WT= 83.82kg ±8.06) were all male high performance athletes participating at the varsity level. All subjects participated in a 20-minute warm up on a Concept 2 rowing ergometer before participating in a 6000 meter timed trial at maximum effort. After 24 hours of recovery subjects were required to participate in a 10-minute warm up (run) before being tested for their 5 Repetition Max (RM) on both SQ and DL. A Pearson correlation was used to analyze data and significance was noted at p\u3c.05. Results: Analysis yielded a negative correlation between WT and ET (p=.002 R= -.70), SQ and RS (p\u3c.001 R=-.79), and DL and ET (p=.045 R=-.51). There was no significance at p\u3c.05 for HT and ET. Conclusion: Rowing technique is extremely dependent on the athlete’s ability to maximize leg thrust, therefore making the SQ and DL essential in determining ES. ES was also faster when subject’s WT was heaver which may be due to increased muscle mass in heavier athletes. Addition studies of larger test groups and 1-RM may be required

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.Comment: 28 pages, 10 figures, sumitted to American Journal of Physic

Influence of a humidor on the aerodynamics of baseballs

We investigate whether storing baseballs in a controlled humidity environment significantly affects their aerodynamic properties. To do this, we measure the change in diameter and mass of baseballs as a function of relative humidity (RH) in which the balls are stored. We then model trajectories for pitched and batted baseballs to assess the difference between those stored at 30% RH versus 50% RH. The results show that a drier baseball may be expected to curve slightly more than a humidified one for a given pitch velocity. We also find that the aerodynamics alone would add ~2 feet to the distance a moister ball is hit. However, this is compensated by a ~6 foot reduction in batted distance due to the well known change in coefficient of restitution of the ball. We discuss consequences of these results for baseball played at Coors Field in Denver, where baseballs have been stored in a humidor at 50% RH since 2002.Comment: 21 pages, 7 figures, modified and re-posted 2/2

Preheating of a battery module in an EV

The use of lithium-ion batteries for electric vehicles (EVs) shows excellent promise due to their outstanding properties regarding high energy and power densities, long service life, low self-discharge and rare pollution. However, the performance and life cycle of such batteries depend on the operating temperature as they are extremely sensitive not only to high but also to low temperatures. The climatic conditions of Kazakhstan and in particular, the north part of the country are quite extreme. Temperatures may drop below -40ºC in winter time. For a battery pack of an EV to perform in the most effective way, temperature management is very important. The proposed thermal management system will maintain a battery pack at an optimum average temperature range with an even temperature distribution throughout the module. In this part of the work particular attention paid to the preheating process

Fano effect in a ring-dot system with tunable coupling

Transport measurements are presented on a quantum ring that is tunnel-coupled to a quantum dot. When the dot is in the Coulomb blockade regime, but strongly coupled to the open ring, Fano line shapes are observed in the current through the ring, when the electron number in the dot changes by one. The symmetry of the Fano resonances is found to depend on the magnetic flux penetrating the area of the ring and on the strength of the ring-dot coupling. At temperatures above T=0.65 K the Fano effect disappears while the Aharonov-Bohm interference in the ring persists up to T=4.2 K. Good agreement is found between these experimental observations and a single channel scattering matrix model including decoherence in the dot.Comment: 9 pages, 6 figure

Analytical modelling of planar potential and current distributions in electrodes of lithium-Ion batteries

Mathematical modelling can play an important role in the design of a lithium-ion cell in that many design iterations can be performed at relatively little cost. • Electrochemical models are useful for cell design and optimization but can be typically high-order and complex and hence computationally expensive, and, are therefore not suitable for real-time applications. • Much reduced order electrochemical models for lithium-ion cells have been developed, with these type of models more suitable for use with real-time on-board electronic control units. • However, a difficulty with these methods is that the current-voltage behavior for different operating conditions cannot be predicted

Forage Evaluation of Crested Wheatgrass

An experiment evaluated the forage value of crested wheatgrass (CWG) harvested throughout the grazing season near Sidney, Nebraska over a two-year period (2019-2020). The purpose of the evaluation was to determine forage quality and rumen undegradable protein (RUP) content to help producers with supplementation decisions for cattle grazing monoculture CWG pastures. In vitro dry matter disappearance quadratically decreased from 54% in May to 37% in September of 2019, with no changes throughout 2020, averaging 43%. In both years, crude protein (CP) decreased throughout the growing season while rumen undegradable protein (RUP) increased (as % CP). Digestible RUP was less than 0.50% of DM for all samples collected. Producers with cattle grazing CWG monoculture pastures could use these data to assist with supplementation decisions