A variable drag coefficient,spatially extended numerical model of hammer throws and new wind tunnel data on current hammers

The maximum distance a hammer can be thrown depends on its mass, length and aerodynamic drag, meaning that record hammer throws performed before and after a rule change (for example, if the minimum mass is changed) cannot be compared directly. However, if all factors affecting the flight of a hammer are fully understood, and the range travelled by a hammer thrown with a given initial speed, angle and release height can be predicted, records thrown under different rules can be compared. In this work, a numerical model is developed, which includes the effects of atmospheric pressure, altitude, Coriolis Effect, gravitational variation, wind speed, ambient temperature, linear drag, torsional drag, hammer size and hammer orientation. It is based on the model of Mizera and Horvath (J Biomech 35:785–796, 2002). Two refinements are made: the drag coefficient varies with Reynolds number, and the hammer is represented as a spatially extended object with nonzero moment of inertia. New wind tunnel data on the drag of the three main components of the hammer (ball, cable and handle) are presented. This data are incorporated into the model which is then used to predict throws made at the IAAF 2011 World Athletics Championships (Daegu, Korea). The model is shown to be capable of predicting to within 1 % the distance of hammer throws where the air density, latitude, release height, release angle and release velocity are known. It is more accurate than numeric and analytic models which assume a constant drag coefficient. This may be because it does not require the user to choose the drag coefficient and automatically uses an appropriate drag coefficient regardless of conditions. With a good biomechanical model or good assumptions about release speeds, throws with different implements can be compared to compare records thrown before and after rule changes. Further work is needed to develop a biomechanical model capable of predicting the release speed an athlete can achieve with a range of different implements.     

Practical Guides

HUMAN FACTORS IN FORMS DESIGN by John H. Burgess (Chicago: Nelson-Hall, 1984---$22.95)

PHOTOJOURNALISM: NEW IMAGES IN VISUAL COMMUNICATION by Philip C. Geraci (Dubuque, Iowa: endall/Hunt Publishing, 1984---$22.95, paper)

AUDIO CONTROL HANDBOOK FOR RADIO AND TELEVISION BROADCASTING by Robert S. Oringel (New York: Hastings House, 1983---$14.95, paper)

FUNDAMENTALS OF NEWS REPORTING by Ralph S. Izard, et al. (Dubuque, Iowa: Kendall/Hunt, 1983---$12.95, paper)

BROADCAST NEWS WRITING, REPORTING, AND PRODUCTION by Ted White, et al. (New York: Macmillan, 1984---price not given)     

PERSPECTIVES ON OLDER ADULTS IN PHYSICAL ACTIVITY AND SPORTS

Older Canadian adults are showing increasing interest in physical activity participation as evidenced by the appearance of masters’ levels in sport clubs and the proliferation of seniors programs in a wide variety of settings. Thousands of seniors are participating in Seniors’ Games competitions across Canada, and in this late‐life pursuit of excellence, they seek quality instructional help and supervision. There has been increasing demand for instructors for the older age groups. Surprisingly, little attention has been paid to instructional issues by the various professional groups most likely to be involved with seniors. This paper addresses the problems and challenges facing prospective leaders and educators of the older adult in physical training and acknowledges the pitfalls of exercise leaders who are inexperienced in dealing with aging adults. Citing real‐life experiences and observations across a number of high‐performance and vigorous exercise settings, this article illuminates some of the difficulties facing both physical educators and older adults and confirms the idea that educational gerontology is often a matter of mutual learning. Overall, a problem of everyone underestimating the potential for learning in the later years, particularly with respect to physical learning, is likely to reinforce stereotypes of frailty as a natural outcome of aging processes.     

A framework to support group essay writing in English for Academic Purposes: a case study from an English-medium instruction context

In English for academic purposes courses, group oral presentations are quite common but essay writing tends to be seen as an individual endeavour, albeit with scope for peer review. This article discusses action research reflecting on student perceptions of a framework to support students through a semester-long collaborative essay assignment in an English-medium instruction university in Macau. The framework presented incorporates collaborative and individual assignment tasks, assisted by information and communications technology, to support the collaborative process and facilitate the assessment of the individual within the group. Even though writing in a group may take more time and effort, it is viewed favourably by the majority of students due to the additional learning gains to be made by writing collaboratively, including the increased quality of ideas and the social interactions (face-to-face and online) required to come to agreement.