Angular Kinematics

Question 1

angular/rotational motion

Answer 1

all parts of the body/object move along a circular path about an axis

Question 2

internal axis

Answer 2

axis through hip joint

Question 3

external axis

Answer 3

gymnastics bar

Question 4

real axis (and internal)

Answer 4

bike wheel

Question 5

imaginary axis

Answer 5

track

Question 6

absolute angles

Answer 6

measured from immovable line (constant)

Question 7

relative angles

Answer 7

measured between segments

Question 8

clockwise (CW) movement

Answer 8

negative

Question 9

counterclockwise (CCW) movement

Answer 9

positive

Question 10

right hand rule

Answer 10

• fingers curl in the direction of the rotation
• thumb = vector representing motion

Question 11

what is general motion?

Answer 11

combination of linear and angular motion

Question 12

measuring joint angles - flexion

Answer 12

positive (exception: knee)

Question 13

measuring joint angles - extension

Answer 13

negative

Question 14

why is the Q-angle larger in women than men?

Answer 14

wider pelvis relative to leg length

Question 15

large Q-angle

Answer 15

patellofemoral pain due to extreme patellar tracking

Question 16

radian

Answer 16

size of the angle when the arc length is equal to the radius (57.3 degrees)

Question 17

how many pi are in a circle? (360 degrees)

Answer 17

2 pi

Question 18

angular position (θ)

Answer 18

orientation of a line w respect to another line or plane

Question 19

angular displacement (Δθ)

Answer 19

difference in the initial and final angular positions

Question 20

avg angular velocity (ω)

Answer 20

rate of change in angular position

Question 21

angular speed

Answer 21

angular distance / change in time

Question 22

avg angular acceleration (α)

Answer 22

rate of change of angular velocity

Question 23

is angular displacement a vector quantity?

Answer 23

yes

Question 24

angular distance

Answer 24

sum of all angular changes

Question 25

angular displacement

Answer 25

difference between the initial and final positions

Question 26

positive angular acceleration

Answer 26

- increasing angular velocity in the + direction - decreasing angular velocity in the - direction

Question 27

negative angular acceleration

Answer 27

- increasing angular velocity in the - direction - decreasing angular velocity in the + direction

Question 28

what is the slope of an angular position vs time graph?

Answer 28

angular velocity

Question 29

what is the slope of an angular velocity vs time graph?

Answer 29

angular acceleration

Question 30

inexperienced paddle boarders

Answer 30

shoulder ROM > hip ROM

Question 31

experienced paddle boarders

Answer 31

greater shoulder motion & elbow extension positions at end of paddle stroke

Question 32

experienced batters, pitchers, tennis players

Answer 32

faster joint angular velocities

Question 33

how can athletes increase performance?

Answer 33

faster segment movement = faster movement of ball, bat, etc.

Question 34

how does the rotation of the limb affect the object?

Answer 34

increase radius > increase curvilinear distance > increase velocity

Question 35

curvilinear distance (s)

Answer 35

Δs = rΔθ m = (m)(radian)

Question 36

greater radius

Answer 36

greater linear distance traveled

Question 37

curvilinear velocity (VT)

Answer 37

VT = rω m/s = (m)(rad/s)

Question 38

T/F: as a n object rotates around an axis, all parts of the object rotate at the same angular velocity but at different linear velocites

Answer 38

True

Question 39

what does the linear velocity of a rotating point depend on?

Answer 39

its distance from the axis of rotation

Question 40

T/F: as an object rotates around an axis, all parts of the rigid object rotate at the same angular velocity but at different linear velocities

Answer 40

True

Question 41

an object is accelerating when it is:

Answer 41

- speeding up or slowing down (change in velocity) - changing direction

Question 42

what is the angular acceleration when the angular velocity is constant?

Answer 42

angular accel = 0

Question 43

tangential acceleration (aT)

Answer 43

linear acceleration of a point on a rotating object that acts tangentially to the path

Question 44

when is tangential acceleration not zero?

Answer 44

when a point is speeding up or slowing down (represents change in linear v)

Question 45

radial (centripetal) acceleration

Answer 45

- toward center of circle, axis of rotation - represents change in direction

Question 46

is more or less force needed to produce radial acceleration?

Answer 46

more force

Question 47

two factors that make it difficult to stay on a curved path:

Answer 47

1) smaller radius 2) greater tangential velocity

Question 48

is there an angular acceleration when the angular velocity is constant?

Answer 48

No, constant angular velocity = no angular acceleration

Question 49

is there linear acceleration when the angular velocity is constant?

Answer 49

Tangential acceleration: no Radial acceleration: yes, because there will still be a change in direction so the object experiences accel.

Question 50

projectile at release

Answer 50

- tangential acceleration becomes zero - radial acceleration becomes zero - VT = VRi

Question 51

are tangential and radial accelerations parallel or perpendicular to one another?

Answer 51

perpendicular

Question 52

if angular velocity is constant

Answer 52

- tangential velocity is constant - acceleration = 0

Question 53

if angular acceleration is zero

Answer 53

- tangential acceleration = 0 - radial accel. and tangential vel. will have magnitudes