Pk3 : CH2 Linear Kinematics

Kinematics (form or technique)

branch of dynamics concerned with the description or appearance of motion

Linear Kinemaics

the study of the shape, form, pattern, and sequencing of linear movement through time, without particular reference to the force that cause or result from the motion

Linear Motion (translation)

All pts on a body or object move the same direction, distance and time

Rectilinear Translation

no change in direction of motion or object

ex: hockey played gliding on ice

Curvilinear Translation

constant change in direction of motion of the body or object ex

ex: skydiver in free fall

Angular Motion

All pts on body or object move in circles about the same fixed central line

ex: gymnast on a high bar = rotation of joints

General Motion

Combo of linear and angular motion * peddling a bike or walking

Position

location in space relative to space

• ordinarily system

Units of Length

Distance and displacement

Distance

measure of lent path followed start to finish

Displacement

vector quantity (size and direction) - resultant displacement = straight line start to finish in comparison actual movements

What is Displacement

d(y)=y(f)-y(i)

d(x)=x(f)-x(i)

What sports is displacement more important than distance traveled

Soccer and Football

Speed

rate of motion (#), scalar quantity

use to describe how fast a distance travels

Velocity

Change in position or displacement that occurs during a given period for time in a specific direction

DV=displacement (d)/ Dt (change in time)

Acceleration

rate of change in velocity

• speed of an object

• magnitude or direction change

Projectile

a body in free fall that is only subset to forced of gravity and air resistance

Is an airplane a projectile?

No, they are influenced by additional forces

If you drop is dropped straight down from 1m high, and a baseball is hit from 1m high, do they strike the ground at the same time?

yes, if they are the same mass and dropping at the same height, they will hit the ground at the same time

Gravity produces a ?

a constant downward vertical acceleration of -9.8

Projection Angles

Vertical - straight up and down

Oblique - angle between 0-90*

Horizontal - projected at 0*

Projection Speed

When projection angles and other factors are constant the projection speed determines the length/size of the projectiles trajectory

ex: vertical jump performance expends on takeoff speed

Relative Projection Height (RPH)

difference in height from which the body is initially projected and the height a which it lands or stops

ex: a golf ball will be teed up higher to increase distance

When RPH is 0, the angle or projections that is produces a max horizontal displacement of 45*

Projection Initial Velocity

used both intial speed (magnitude) and the angle of projection (direction) into a single vector