A dynamic approximation of balanced gymnastics landings

A gymnast can balance after an uneven parallel bar dismount by contacting the ground with an appropriate body position and angular velocity. Balanceable gymnastics landings were predicted by dividing landing into two parts: a short duration impact phase when foot-mat contact forces are high, and a subsequent longer balancing phase during which the gymnast exerts active control at the joints to attenuate the resulting post-impact velocities and achieve a desired motionless terminal configuration. This paper identifies controllable sets of pre-impact landing positions and velocities for a typical female collegiate gymnast that are feasible targets for the end of flight following a single- and double-backward somersault uneven bar dismount with forward mass centre (CM) velocity. Simple algebraic impulse-momentum models for the impact phase determine impulses necessary to stop the feet and slow angular velocity. After impact, a dynamic analysis is needed to determine stability because non-negligible post-impact angular and linear velocities are possible. For almost all successfully balanced landings, ground contact occurs with the CM positioned above the feet and between the toe and heel, because the linear impact impulses that stop the feet also contribute to an angular impulse that slows angular momentum. Only at the largest pre-impact angular velocities following a double-somersault dismount can contact occur with the CM in front of the toe. The gymnast is in balanceable preimpact orientations longer when rotating more slowly and with a smaller angular momentum; therefore balance may be more likely after performing a single-somersault dismount with a large moment of inertia.     

Urban classroom conflict: Student-teacher perception: Ethnic integrity,solidarity, and resistance

This study compared student-teacher perception of discipline; inquired if it were interpersonal, procedural, or substantive; and examined how ethnicity, achievement, gender, and position influenced practice. Gay's (1981) theory about interethnic group interactions, combined with perceptual disparity and cultural discontinuity, provided the conceptual framework. Data sources were interviews, classroom observations, and school records. Students (N=16), African American, Chicano, European American, and Filipino, and teachers (N=9) from an urban high school participated. The data analysis revealed that interpersonal conflicts were more consequential for students of color. Evidence of disparate perceptions among ethnically diverse students and teachers surfaced. The attitudes, beliefs, and values of students and teachers differed and were associated with ethnicity, gender, and level of academic achievement.     

California's emergency credential teachers: examining program conditions for sustainability and effectiveness

The Summer Institute for Teacher Education (SITE), a one-year program, emerged in response to a California State University directive to increase the number of credentialed teachers. This article explains the rationale and program approach, describes the participants of the first two cohorts—SITE 1999 and SITE 2000, and uses yearly program evaluations to discuss the program goals and outcomes. It concludes with implications for the preparation of teachers of color and the institutional conditions needed to promote sustainability and teacher effectiveness. Three goals differentiated SITE from the regular program: (1) to create a one-year credential program to increase the yearly number of credentialed elementary teachers, (2) to offer a program for training the growing number of California's emergency credentialed teachers, and (3) to provide the contextual conditions and?culturally responsive curricular content needed for successful sustained service to children, especially those attending high-poverty, low performing urban schools.