Biomechanics_notes_for_Midterm-1-1

# Biomechanics_notes_for_Midterm-1-1 - Chapter 1 Kinematic...

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Chapter 1 Kinematic description- description of human movement accomplished by using words position, velocity, and acceleration. Ignores causes of motion. -most commonly used measurement system is metric system. International metric system is SI system ( 7 base units…length(m), mass(kg), time(s), electric current(A), temp(K), amount of substance (mol), luminous intensity (cd)) Kinetics- effect of a force: force, impulse, energy Anthropometrics - mechanical properties of body segments: segment length, mass, center of mass. Digits in a number that help indicate accuracy are significant figures Movement can either be described by displacement or by rate (velocity and acceleration) Position is location of object in space relative to a baseline value. Motion- change in position and displaced. Detected when compared to objects position. Displacement- spacial element of motion. Change in position. Velocity- vector quantity, change in position with respect for time. Tells how fast and in what direction. Speed- does not show direct, just how fast. Slope: shows rate of change. Steeper the slope, more change. -downward slope = negative velocity Acceleration- vector quantityrate of change of velocity = change in velocity / change in time (ex. A dropped ball changes velocity) A=change in velocity/ change in time Vf=Vi + at We can collect kinematic data with cameras. (frame rate set at 10 frames per sec for sprinter) Digitizer – (pg 14) capable of determining the x-y coordinates of the selected landmarks.

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(pg. 11) *to find the distance an object travels we can use an equation derived from the definition of velocity. Average velocity = (change in position) / (change in time) Vf +Vi / (2) = rf-ri / (t) rf- ri = ((Vi+at+Vi)/(2)) * (t) rf-ri = ((2Vi+at)/(2)) *t rf-ri= Vit +1/2 at^2 This equation shows that displacement of an object depends on: initial velocity (Vi), acceleration (a), and time (t). Vf^2 = Vi^2 + 2a(rf-ri) avg velocity = (change r) / (change t) *Up and Down pg. 15* Characteristics of a projectile: -parabolic due to gravity -no horizontal acceleration -vertical velocity has greatest absolute value at beginning and end of flight The time of flight for a projectile depends on the vertical velocity at release When release and landing heights are the same the optimum angle is 0.785 radians. As the release height increase, the optimum angle decreases. Height= 1/2a(Vi * [email protected]) ^2 Flight Time = 2/a (Vi * [email protected]) Distance = 2Vi^2 / a ([email protected])([email protected]) 1rad = 57.3 deg Displacement and Acceleration do not always act in the same direction, so it is not possible to tell the direction of acceleration from the direction of movement. 2 steps in position-time graph: 1. Identify minima and maxima in position-time graph: rate of change has value of zero Maxima- peaks Minima- valleys 2. slope estimation
Scalars and Vectors (pg. 22) Vectors- quantities that display magnitude and direction . (ex. Displacement, velocity, acceleration, force, momentum, torque) Direction of vector is its

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Biomechanics_notes_for_Midterm-1-1 - Chapter 1 Kinematic...

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