Effects of swing-weight on swing speed and racket power

Abstract

Measurements are presented of the speed at which six different rods could be swung by four male students. Three of the rods had the same mass but their swing-weight (i.e. moment of inertia) differed by large factors. The other three rods had the same swing-weight but different masses. Our primary objective was to quantify the effects of mass and swing-weight on swing speed. The result has a direct bearing on whether baseball, tennis, cricket and golf participants should choose a heavy or light implement to impart maximum speed to a ball. When swinging with maximum effort, swing speed (V) was found to decrease as swing-weight (I _o) increased, according to the relation V?=?C/I _o ⁿ , where C is a different constant for each participant and n?=?0.27 when I _o >?0.03 kg?·?m². Remarkably similar results were obtained previously with softball bats (where n?=?0.25) and golf clubs (where n?=?0.26). Swing speed remained approximately constant as swing mass increased (when keeping swing-weight fixed). The implications for racket power are discussed.     

Three‐year results of the Friendly Schools whole‐of‐school intervention on children's bullying behaviour

A group randomized controlled trial tested the efficacy of the Friendly Schools program to reduce student bullying behaviour. This socio‐ecological intervention targeted the whole school, classroom, family, and individual students to reduce bullying behaviour. Self‐report data were collected in 29 schools over three years from a cohort of 1968 eight to nine‐year‐olds. Surveys measured frequency of being bullied, bullying others, telling if bullied and observing bullying. Results indicate that intervention students were significantly less likely to observe bullying at 12, 24 and 36 months and be bullied after 12 and 36 months, and significantly more likely to tell if bullied after 12 months than comparison students. No differences were found for self‐reported perpetration of bullying. The findings suggest whole‐of‐school programs that engage students in their different social contexts appear to reduce their experiences of being bullied and increase their likelihood of telling someone if they are bullied.     

A Critical Challenge: The Engagement and Assessment of Contingent,Part-Time Adjunct Faculty Professors in United States Community Colleges

In 2011, according to a National Center for Education Statistics report, part-time instructional staff in all higher education institutions exceeded full-time faculty members for the first time, accounting for 50% of all instructional staff (National Center for Education Statistics [NCES], 2012 National Center for Education Statistics . ( 2012 ). IPEDS, Digest of education statistics, Winter 2011–12, human resources component, fall staff section: Table 286 [data file]. Retrieved from http://nces.ed.gov/programs/digest/d12/tables/dt12_286.asp  [Google Scholar]). The same report indicates part-time faculty in community colleges exceeds 70% of instructional staff. Perhaps more alarming are the numbers of contingent instructional staff—faculty without long-term employment commitments. According to this measure, nearly 70% of faculty members in all areas of higher education have little-to-no job stability (American Association of University Professors [AAUP], 2013 American Association of University Professors (AAUP) . ( 2013 ). Background facts on contingent faculty. Retrieved from http://www.aaup.org/issues/contingency/background-facts  [Google Scholar]; Schuster & Finklestein, 2006 Schuster , J. H. , & Finklestein , M. J. ( 2006 ). The American faculty: The restructuring of academic work and careers . Baltimore , MD : The Johns Hopkins University Press . [Google Scholar]). However, limited research exists on the working experiences of this major subpopulation of United States professors.

The purpose of this qualitative study was to explore the experiences of part-time contingent community college faculty regarding the assessment processes their institutions implemented. Through interviews, researchers gathered data identifying what 20 part-time contingent faculty professors reported regarding teaching conditions and institutional assessment procedures. Participant interviews revealed two major themes centered on a lack of institutional engagement and meaningful assessment policies or procedures.     

String tension effects on tennis ball rebound speed and accuracy during playing conditions

The primary aim of this study was to determine whether variations in rebound speed and accuracy of a tennis ball could be detected during game-simulated conditions when using three rackets strung with three string tensions. Tennis balls were projected from a ball machine towards participants who attempted to stroke the ball cross-court into the opposing singles court. The rebound speed of each impact was measured using a radar gun located behind the baseline of the court. An observer also recorded the number of balls landing in, long, wide and in the net. It was found that rebound speeds for males (110.1+/-10.2 km.h-1; mean+/-s) were slightly higher than those of females (103.6+/-8.6 km.h-1; P<0.05) and that low string tensions (180 N) produced greater rebound speeds (108.1+/-9.9 km.h-1) than high string tensions (280 N, 105.3+/-9.6 km.h-1; P<0.05). This finding is in line with laboratory results and theoretical predictions of other researchers. With respect to accuracy, the type of error made was significantly influenced by the string tension (P<0.05). This was particularly evident when considering whether the ball travelled long or landed in the net. High string tension was more likely to result in a net error, whereas low string tension was more likely to result in the ball travelling long. It was concluded that both gender and the string tension influence the speed and accuracy of the tennis ball.     

Age-related incidence curve of hospitalized Shaken Baby Syndrome cases: convergent evidence for crying as a trigger to shaking

OBJECTIVE: To determine whether there is an age-specific incidence of hospitalized cases of Shaken Baby Syndrome (SBS) that has similar properties to the previously reported "normal crying curve," as a form of indirect evidence that crying is an important stimulus for SBS. DESIGN AND SETTING: The study analyzed cases of Shaken Baby Syndrome by age at hospitalization from hospital discharge data for California hospitals from October 1996 through December 2000. PATIENTS: All cases of children less than 18 months (78 weeks) of age for whom the diagnostic code for Shaken Baby Syndrome (995.55) in the International Classification of Disease, Ninth Edition, Clinical Modification was assigned. RESULTS: There were 273 hospitalizations for SBS. Like the "normal crying curve," the curve of age-specific incidence starts at 2-3 weeks, has a clear peak, and declines to baseline by about 36 weeks of age. In contrast to the normal crying curve that peaks at 5-6 weeks, the peak of SBS hospitalizations occurs at 10-13 weeks. CONCLUSIONS: The age-specific incidence curve of hospitalized SBS cases has a similar starting point and shape to the previously reported normal crying curve but the peak occurs about 4-6 weeks later. Of the likely predisposing causes, this pattern is only consistent with the properties of early crying. There are numerous explanations for the lag in the peaks between crying and SBS hospitalizations, including the possibility of repeat shakings prior to hospitalization. The importance of crying as a stimulus to SBS may provide an opportunity for preventive intervention.     

EDITORIAL

Novice nurses encounter numerous factors that impact on their learning in the complex healthcare workplace. Registered nurses often work one‐on‐one with novices as preceptors to facilitate the development of novices’ clinical skills and socialisation into the profession. This paper explores the concept of preceptorship from novice nurses’ and preceptors’ perspective, drawing upon data from a project between a large healthcare organisation and a university in Melbourne, Australia. The study, framed in ethnomethodology, included fieldwork observation, interviews and student surveys; this paper focuses on data collected over a series of individual interviews with nursing students (n = 28) and preceptors (n = 25). Thematic analysis yielded six key themes: workplace socialisation, empathy, individuality, willingness to engage, changing support and a realisation [by novices about the preceptor role]. Findings highlight the complexity of workplace learning that is influenced by the idiosyncrasies of the individuals involved and the social milieu in which the learning takes place.     

Do emotional and behavioural difficulties in primary school predict adolescent victimisation trajectories?

Chronic victimisation in adolescence is a traumatic experience with potential negative long-term health consequences. Given that victimisation has been shown to increase over the transition from primary to secondary school, longitudinal data from 1810 students transitioning from primary to secondary school were used to identify victimisation trajectory groups; classified as low-increasing, low-stable, medium-stable and not-bullied. Males with emotional and behavioural difficulties (both internalising and externalising behaviours) and females with externalising behaviours were more likely to be in the increasing and stable victimised groups than the not-bullied group. The results of this study suggest whole-school bullying intervention programmes need to occur before students reach secondary school, and that transition programmes need to emphasise and support social interaction between peers to reduce victimisation and the harms caused by long-term exposure to bullying.