Mechanics of Human Movement UARK EXAM 1

Biomechanics

study of the forces and movements of force acting on and produced by living bodies

Mechanics

branch of physics that analyzes the actions of forces and particles of mechanical systems

Rigid Body

a system of particles (i.e. a body) which does NOT deform

Rigid Body Mechanics

application of mechanical principles to a rigid body or system of rigid bodies

Statics

study of rigid bodies or systems that are in a state of of constant motion (at rest or moving at a constant speed)

Dynamics

the study of rigid bodies or systems that are subject to acceleration

Kinematics (aka the WHAT)

description of motion as a function of space and time WITHOUT reference to forces causing the motion; describes what motion is happening without worrying about the forces behind it

Kinetics (aka the HOW)

relationship between forces acting on a rigid body or system and the motion of that rigid body or system; how and why a motion is happening

Deformable Body

a body that changes its shape and/or volume when acted upon by a force

Deformable Body Mechanics

application of the principles of mechanics to a deformable body

Elasticity

propensity of material to return to original shape when deformed

Plasticity

propensity of material to undergo permanent deformation when loaded

Viscoelasticity

material exhibits both viscous and elastic characteristics when deformed (i.e. dependent on loading rate)

Fluid Mechanics

application of the principles of mechanics to fluids (liquids to gases)

Mass

quantity of matter in a body regardless of its volume or the forces acting on it

Rectilinear

linear motion along a straight line

Curvilinear

linear motion along a curved line

Linear Motion

motion along a line with all parts of the body moving the same distance in the same direction at same time

Angular Motion

all parts of the body move in a circle about a central line or point (axis of rotation)

Vector

A quantity that has magnitude and direction

Scalar

A quantity that has only magnitude

3 Basic Quantities with SI Units

length: meters (m)

time: seconds (s)

mass: kilograms (kg)

Linear Kinematics

The kinematics of particles, objects, or systems undergoing linear motion

Linear Displacement

difference between initial and final positions: independent of the path (vector)

Distance Travelled

length of a path (scalar)

Speed

distance/time

Linear Velocity

rate of change of linear position with respect to time

-rate at which a body moves from one position to another

Linear Acceleration

rate of change of linear or angular velocity with respect to time

Vector Decomposition

knowing magnitude(V) and orientation(theta)

Average Velocity

changes in direction occur

Instantaneous Velocity

specifies how fast and in what direction one is moving at one particular point in time

-magnitude of instantaneous velocity is exactly the same as instantaneous speed

Linear Acceleration can cause

-a change in magnitude of velocity WITHOUT changing the direction of velocity

ex: car accelerating or decelerating

-a change in direction of velocity WITHOUT changing the magnitude of velocity

ex: kicking soccer ball back at someone with the SAME velocity

-a change in direction AND magnitude of velocity

ex: someone passing you a soccer ball and then you striking it really hard at the goalie

Propulsion

magnitude and velocity increases

-object speeds up or accelerates

Braking

magnitude and velocity decrease

-object slows down or decelerates

No Acceleration

constant velocity

ex: cruise control

Projectile

a body in free fall that is subject only to the forces of gravity and air resistance

what is part of the laws of projectile motion?

center of mass

Projectile Motion

-how well someone is performing

objects acting as projectiles

soccer, basketball, baseball, archery, golf ball, etc

body acting as projectile

high jump, long jump, gymnastics, falls, etc

Performance variables of interest

-flight distance

-flight time

-maximum height

Gravity

- 9.81 m/s^2

3 Factors influence projectile trajectory

-projection angle (launch angle)

-projection speed (actual magnitude)

-relative height of projection