Exam two Flashcards
explain COM and its importance to human motion, sports, and/or coaching
COM-fictitious point representing the mean position of the matter of all the body; the point in a body at which the mass of the system may be considered to be concentrated at a single point. The three reasons it’s so important is because it represents our whole body (performance, parabolic flight path), it represents body symmetry (performance, balance), and it gives us cues to external loading (injury, safety). For qualitative analysis (coaching) it help understand the whole body position in terms of balance and performance. In biomechanics analysis, it provides the context by which we attempt to accelerate or decelerate the body and provides the point of application of gravitational force.
what are internal and external forces with regard to the human body. Draw a free body diagram pf a human sprinting with one leg in contact with the ground and pushing off to accelerate his COM forward. Draw and label all external forced acting on his body. Describe what internal forces the athlete must use to generate/oppose these external forces.
internal forces: From structures within our body like muscles tensile(apart) compressive (together)
external forces: forces that act on our body by the environment. non-contact (gravity) and contact (fluid, air, ground)
what are normal and frictional forces. How are horizontal and frictional forces at takeoff important to heigh or distance of a jump? How do these affect COM motion during a sports movement.
Normal force: acts perpendicular to the surface it contacts (vert)
frictional force: acts parallel to the surface it contacts (horizontal). Horizontal (frictional) forces are important for distance. Vertical (normal) forces are important for height. Frictional forces are increased by normal forces but there has to be some frictional force.
muscles can only create linear (straight line) forces that have magnitude and direction; these can be resolved into their individual component force vectors; what do these individual component force vectors represent with regard 6 degrees of freedom motion and joint stability.
torques are responsible for rotation. 3 degrees of rotation for ever movement. Individual component force vectors come from translations and that’s the other three degrees. A knee slides(translation) and rotates.
define linear position, velocity, and acceleration and what are the differences between these and distance, displacement, and speed quantities.
linear position-location in space (point a to b in straight line)
linear velocity-rate of change of position over time
linear acceleration-change in velocity over time
These are all vectors while speed and distance are scalar.
define angular position, velocity and acceleration
angular position-location in space just angular position in degrees
angular velocity-rate of change of position over time in degrees (how long it takes something to rotate through angular displacement)
angular acceleration-change in angular velocity over time in degrees.
