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Flashcards in Linear Kinematics Deck (25)
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1

Kinematics

Description of the spatial and temporal components of motion
Involves position, velocity and acceleration of a body without concern for the forces which cause motion

2

Quantities

Scalar
Vectors

3

Scalars

fully described by their amount or magnitude
Ex: Distance, time, position

4

Vectors

described by both magnitude and direction
Ex: Displacement, Velocity, Acceleration

5

Motion

1. Linear Motion
Translation
2. Angular Motion
Rotation
3. General Motion
Combination of translation and rotation

6

Linear Motion Example

Curvilinear
Rectilinear

7

Rectilinear Examples

Box pushed along ground
COM path during:
100m sprint
Ice skating, skateboard..
Bicycling

8

Curvilinear Examples

Path of ball in air
COM path during:
Long jump
Diver
Ski jumper

9

General Motion

Combination of linear and angular motion
Most common type of motion in sports and human movement

10

Angular Motion Exp.

Gymnast swinging around high bar
Joint motion
Not all joints (i.e. plane/gliding joints)
Ball spinning in air
Diver (spinning)

11

General Motion Exp.

Ball in air
Path of ball = curvilinear
Spinning ball = angular
Diver
Path of COM = curvilinear
Rotating/Spinning body = angular
Sprinter
Path of COM = rectilinear
Joint motion = angular

12

Reference system

Cartesian (Rectangular) Coordinate System
Fixed point (origin)
Axes are perpendicular
2-D or 3-D System:
2-D: x (horizontal), y (vertical) axes
Distance from respective axis
2-D used when motion is primarily in one plane
3-D System: x, y, z axes
3rd axis provides depth
Complicated

13

Measuring Motion

Assume body is a rigid structure

Place markers on body segments

Record motion

Digitize markers relative to coordinate system
One frame at a time

14

Distance

Length of path followed by object from initial to final position
Scalar quantity (only magnitude)
Not necessarily a straight line

15

Displacement

Straight line distance in a specific direction from initial to final position
“as the crow flies”
Vector quantity

displacement = positionfinal – positioninitial

16

Speed

Rate of motion
speed = Δdistance / Δtime
Scalar quantity (magnitude only)

17

Velocity (v)

Displacement of an object over time

v = Δdisplacement / Δtime
v = (df – di) / Δtime

Vector quantity
Greater interest than speed
Direction: negative or positive
Direction of motion influence velocity direction

18

Velocity Types

1. Average velocity

2. Instantaneous velocity
Methods
Central difference method
Smaller time intervals allow for calculation of velocity at a specific point in time
Tangent

19

Acceleration

Is someone described as being “quick” or having “good acceleration” the same as being fast?

NO!
Acceleration describes a person’s ability to change speed or direction, not top speed.

20

Average Velocity

Value over an interval or time
Do not represent max values

21

Instantaneous Velocity

Value at a given moment in time
May represent max values
Magnitude of instantaneous velocity = instantaneous speed
Approach instantaneous measures with small time intervals

22

Projectile Motion

Object in free-fall that is affected only by gravity and air resistance

23

Trajectory

Flight path of a projectile

24

Apex

Highest point of trajectory

25

Release

When the object becomes projectile