Chapter 8- Linear Kinematics
Why be concerned with the description of motion?
The outcomes of many sporting events are kinematic
What is motion?
*Action or process of a change in position *Movement is a change in position
Linear motion
*Is also referred to as translation. *Occurs when all points on a body move:the same distance, the same time *This can happen in 2 ways: 1.Rectilinear translation 2. Curvilinear translation.
Linear motion; Curvilinear translation
*Occurs when all points on a body move in a curved line. *Orientation of object does not change *All points move the same distance *The direction of motion is constantly changing even though the orientation is not changing (throwing a foot ball or long jumping)
Two things are necessary for motion to occur
*Time *Space
Angular motion
*is also referred to as rotary motion or rotation *Occurs when all points on a body move: In circles, About the same fixed central line or axis (Think barstrazz http://www.youtube.com/watch?v=nec543QNe9Y)
Linear kinematics
-Linear kinematics is concerned with the description of linear motion -Why study linear kinematics? -Performance enhancement Clinical analysis -Gait analysis
Summary of Acceleration
-The direction of motion is not necessarily the same as the direction of acceleration.
General motion
-is also referred to as mixed motion -Occurs as a combination of both linear and angular motions -Most common type of motion exhinbited in sports and human movement
Factors influencing Trajectory
Initial conditions of the projectile wil determine what motion the projectile will have -Initial pasition -Initial velocity
Average
Occuring over a designated time interval
Angle of projection
The direction at which a body is projected with respect to the horizontal
Uniform Acceleration
When this occurs, the net external forces acting on an object is constant and unchanging.
Projectile
a body in free fall that is subject only to the forces of gravity and air resistance
Acceleration
a=Δvelocity/Δtime
Speed
change in distance over time
Displacement
change in position *Vector
Horizontal & Vertical Components are
independent of each other.
Gravity
influences the vertical components -9.81m/s^2
Distance
length of a path of motion *Scalar From staring postiton to the ending position along the path
Movements can be classifies as:
linear angular both (known as general)
Instantaneous
occuring during a small interval of time
Linear motion; Rectilinear translation
occurs when all points on a body move in a straight line. *Direction of motion does not change *Orientation of object does not change *All points move the same distance (Example; doing a pull up)
Velocity
the change in positon (displacement) with respect to time Δdisplacement/Δtime
Trajectory
the flight path of a projectile.
apex
the highest point in the trajectory
Range
the horizontal displacement of projectile at landing.
Projection velocity:
the magnitude of projection velocity.
