Flashcards in Linear Kinematics Deck (25)

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1

## Kinematics

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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

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Scalar

Vectors

3

## Scalars

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fully described by their amount or magnitude

Ex: Distance, time, position

4

## Vectors

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described by both magnitude and direction

Ex: Displacement, Velocity, Acceleration

5

## Motion

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1. Linear Motion

Translation

2. Angular Motion

Rotation

3. General Motion

Combination of translation and rotation

6

## Linear Motion Example

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Curvilinear

Rectilinear

7

## Rectilinear Examples

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Box pushed along ground

COM path during:

100m sprint

Ice skating, skateboard..

Bicycling

8

## Curvilinear Examples

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Path of ball in air

COM path during:

Long jump

Diver

Ski jumper

9

## General Motion

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Combination of linear and angular motion

Most common type of motion in sports and human movement

10

## Angular Motion Exp.

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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.

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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

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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

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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

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Length of path followed by object from initial to final position

Scalar quantity (only magnitude)

Not necessarily a straight line

15

## Displacement

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Straight line distance in a specific direction from initial to final position

“as the crow flies”

Vector quantity

displacement = positionfinal – positioninitial

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## Speed

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Rate of motion

speed = Δdistance / Δtime

Scalar quantity (magnitude only)

17

## Velocity (v)

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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

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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

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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

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Value over an interval or time

Do not represent max values

21

## Instantaneous Velocity

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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

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## Trajectory

### Flight path of a projectile

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## Apex

### Highest point of trajectory

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