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.