The higher derivatives of motion are rarely discussed in the teaching of classical mechanics of rigid bodies; nevertheless, we experience the effect not only of acceleration, but also of jerk and snap. In this paper we will discuss the third and higher order derivatives of displacement with respect to time, using the trampolines and theme park roller coasters to illustrate this concept. We will also discuss the effects on the human body of different types of acceleration, jerk, snap and higher derivatives, and how they can be used in physics education to further enhance the learning and thus the understanding of classical mechanics concepts.

In many countries playground design is driven more by safety than developmental benefits. As risk minimisation strategies become more stringent, many researchers and practitioners are questioning whether young children are able to take sufficient risks in play in order for their play experiences to be interesting and developmentally challenging. This study examined the outdoor play choices and risk‐taking behaviour of 38 children (25 boys, 13 girls) aged between 48 and 64 months from Sydney, Australia. Semi‐structured interviews examined children's play preferences and playground equipment usage. Observations of play explored engagement in risk‐taking behaviour. Selection of equipment indicated a strong preference for challenge and excitement. However, the dominant observed play behaviours involved little risk suggesting equipment at these parks provided few opportunities to practice mastery of skills already in their behavioural repertoire, learning new skills or building on current capabilities. The findings have implications for play provision and playground design. RÉSUMÉ: Dans de nombreux pays, la sécurité préside davantage à la conception des cours de récréation que la préoccupation du développement des enfants. Tandis qu'on observe une inflation des stratégies de réduction des risques, un grand nombre de chercheurs et de professionnels se demandent si les jeunes enfants son capables de prendre suffisamment de risques dans leurs jeux afin de rendre ces expériences ludiques intéressantes et porteuses de défis sur le plan du développement. Cet article porte sur les choix de jeux de plein air et les comportements de prise de risque de 38 enfants (25 garçons, 13 filles) âgés de 48 à 64 mois à Sydney, en Australie. Nous avons étudié, à l'aide d'entretiens semi directifs, les préférences ludiques des enfants et leur utilisation des équipements de cours de récréation. Nous avons eu recours à des observations de jeux pour investiguer leur implication dans des conduits de prises de risques. Certains équipements sont préférés pour leurs attraits et défis. Pourtant, les conduites de jeu dominantes présentent peu de prise de risques, ce qui laisse à penser que les équipements offrent peu d'occasion de maîtriser les habiletés déjà acquises, d' en acquérir de nouvelles ou d'en construire à partir des compétences présentes. Les résultats ont des implications quant à l'offre ludique et à la conception des cours de récréation. ZUSAMMENFASSUNG: In vielen Ländern ist die Anlage eines Freigeländes mehr zugunsten von Sicherheit als von Entwicklung bestimmt. Da Strategien zur Minimierung von Risiken zwingender werden, wird seitens der Forschung sowie der Praxis vielfach die Frage gestellt, ob junge Kinder genügend Risiken in einer Weise eingehen können, dass ihre Spielerfahrungen sowohl interessant als auch herausfordernd für sie sind. Diese Studie untersuchte die Auswahlmöglichkeiten des Spielens im Freien sowie Risiken eingehendes Verhalten von 38 Kindern (15 Jungen, 13 Mädchen) im Alter von 48 und 64 Monaten in Sydney, Australien. Mit halbstrukturierten Interviews wurden die Spielpräferenzen der Kinder und die Nutzung der Ausstattung des Freigeländes untersucht. Mit Beobachtungen wurde das Engagement in Risken eingehendem Verhalten beim Spielen exploriert. Die Auswahl der Ausstattung zeigte eine starke Präferenz fur Herausforderung und Aufregung. In die dominanten Spielverhaltensweisen, die beobachtet wurden, wurde jedoch Ausstattung dieser Parks einbebezogen, die wenig Risiken anbot und damit wenig Gelegenheiten, (1) die Beherrschung von Fertigkeiten zu zeigen, die bereits im Verhaltensrepertoire der Kinder vorhanden waren, (2) neue Fertigkeiten zu erlernen oder (3) auf vorhandenen Fertigkeiten aufzubauen. Die Ergebnisse haben Implikationen für Spielangebote und die Planung von Spielplätzen. RESUMEN: En muchos paises el diseño de los parques de juegos es impulsado por la seguridad, más que por las ventajas para el desarrollo. En la medida que las estrategias para minimar los riesgos son más estrictas, muchos investigadores y prácticos cuestionan sí los niños som capaces de arriesgar lo suficiente en sus juegos para que estos sean interesantes y desafiantes para el desarrollo. El estudio examina las conductas riesgosas y la elección de juegos al aire libre de 38 niños (25 niños y 13 niñas) de 48 a 64 meses de edad, de Sidney, Australia. Entrevistas semi‐estructuradas examinaron las preferencias de juego de los niños y el equipaje usado. Observaciones de juegos exploraron el envolvimiento en conductas riesgosas. Elección de equipajes indicaban mayores preferencias por desafios y excitación. Sin embargo, las conductas de juegos dominantes observadas envolvían pocos riesgos, sugeriendo que el equipamiento de esos parques proporcionaban pocas oportunidades de prácticar el dominio de habilidades de sus repertorios conductuales, aprendiendo nuevas habilidades o desarrollando capacidades ya existentes. Los resultados tienen implicaciones para el diseño y suministro de parques de juegos.

Rapid changes in forces and the resulting changes in acceleration, jerk and higher order derivatives can have undesired consequences beyond the effect of the forces themselves. Jerk can cause injuries in humans and racing animals and induce fatigue cracks in metals and other materials, which may ultimately lead to structure failures. This is a reason that it is used within standards for limits states. Examples of standards which use jerk include amusement rides and lifts. Despite its use in standards and many science and engineering applications, jerk is rarely discussed in university science and engineering textbooks and it remains a relatively unfamiliar concept even in engineering. This paper presents a literature review of the jerk and higher derivatives of displacement, from terminology and historical background to standards, measurements and current applications.

High technology and activity levels in the intensive care unit (ICU) lead to elevated and disturbing sound levels. As noise has been shown to affect the ability of patients to rest and sleep, continuous sound levels are required during sleep investigations. The aim of this pilot study was to develop a robust protocol to measure continuous sound levels for a larger more substantive future study to improve sleep for the ICU patient. A review of published studies of sound levels in intensive care settings revealed sufficient information to develop a study protocol. The study protocol resulted in 10 usable recordings out of 11 attempts to collect pilot data. The mean recording time was 17.49 ± 4.5 h. Sound levels exceeded recommendations made by the World Health Organization (WHO) for hospitals. The mean equivalent sound level (LAeq) was 56.22 ± 1.65 dB and LA90 was 46.8 ± 2.46 dB. The data reveal the requirement for a noise reduction program within this ICU.

Martial arts has many benefits not only in self-defence, but also in improving physical fitness and mental well-being. In our research we focused on analyzing the velocity, impulse, momentum and impact force of the Taekwondo sine-wave punch and reverse-step punch. We evaluated these techniques in comparison with the martial arts styles of Hapkido and Shaolin Wushu and investigated the kinematic properties. We developed a sensing system which is composed of an ICSensor Model 3140 accelerometer attached to a punching bag for measuring dynamic acceleration, Kinovea motion analysis software and 2 GoPro Hero 3 cameras, one focused on the practitioner’s motion and the other focused on the punching bag’s motion. Our results verified that the motion vectors associated with a Taekwondo practitioner performing a sine-wave punch, uses a unique gravitational potential energy to optimise the impact force of the punch. We demonstrated that the sine-wave punch on average produced an impact force of 6884 N which was higher than the reverse-step punch that produced an average impact force of 5055 N. Our comparison experiment showed that the Taekwondo sine-wave punch produced the highest impact force compared to a Hapkido right cross punch and a Shaolin Wushu right cross, however the Wushu right cross had the highest force to weight ratio at 82:1. The experiments were conducted with high ranking black belt practitioners in Taekwondo, Hapkido and Shaolin Wushu.

Objectives: To examine national trampoline injury patterns and trends in the context of improved product safety standards and trampoline design modifications. Method: Review of National Hospital Morbidity data. Results: There were an average 1,737 trampoline injuries reported nationally each year from 2002 to 2011. Both injury frequency and rate grew. Statistically significant rate increases were observed among all age groups, although both are highest among children aged 5–9 years. From 2008/09 there is a possible decreasing trend among the 5–9 age group. Falls predominate and 81% of falls result in fracture. Non‐fall injuries increased annually as a proportion of all hospitalised injury although they did not comprise more than 2.4% in any one year. Conclusions: History provides no evidence of an observable effect of voluntary Australian Standards for trampoline safety on population rates for trampoline injury. The major design modification – netted enclosures – could contribute to the risk of injury by leading parents to falsely believe that a netted enclosure eradicates the risk of injury.