Linear Kinematics

Question 1

Kinematics

Answer 1

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

Question 2

Quantities

Answer 2

Scalar

Vectors

Question 3

Scalars

Answer 3

fully described by their amount or magnitude

Ex: Distance, time, position

Question 4

Vectors

Answer 4

described by both magnitude and direction

Ex: Displacement, Velocity, Acceleration

Question 5

Motion

Answer 5

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

Question 6

Linear Motion Example

Answer 6

Curvilinear

Rectilinear

Question 7

Rectilinear Examples

Answer 7

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

Question 8

Curvilinear Examples

Answer 8

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

Question 9

General Motion

Answer 9

Combination of linear and angular motion

Most common type of motion in sports and human movement

Question 10

Angular Motion Exp.

Answer 10

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

Question 11

General Motion Exp.

Answer 11

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

Question 12

Reference system

Answer 12

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

Question 13

Measuring Motion

Answer 13

Assume body is a rigid structure

Place markers on body segments

Record motion

Digitize markers relative to coordinate system
One frame at a time

Question 14

Distance

Answer 14

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

Question 15

Displacement

Answer 15

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

displacement = positionfinal – positioninitial

Question 16

Speed

Answer 16

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

Question 17

Velocity (v)

Answer 17

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

Question 18

Velocity Types

Answer 18

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

Question 19

Acceleration

Answer 19

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.

Question 20

Average Velocity

Answer 20

Value over an interval or time

Do not represent max values

Question 21

Instantaneous Velocity

Answer 21

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

Question 22

Projectile Motion

Answer 22

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

Question 23

Trajectory

Answer 23

Flight path of a projectile

Question 24

Apex

Answer 24

Highest point of trajectory

Question 25

Release

Answer 25

When the object becomes projectile