ANGULAR KINEMATICS

Question 1

most human movements are based on what type of motion

Answer 1

angular
-translation of the human body happens via rotations of our joints

Question 2

angular units

Answer 2

-degrees
-radians
-revolutions

Question 3

what unit must angular quantities be in to translate into a linear quantity

Answer 3

radians

Question 4

1 radian = ___ degrees

Answer 4

57.3

Question 5

1 revolution = ___ degrees

Answer 5

360

Question 6

1 revolution = ___ radians

Answer 6

2pi

Question 7

angular displacement is a scalar or vector

Answer 7

vector

Question 8

angular displacement

rotations in the clockwise direction have what sign

Answer 8

negative

Question 9

angular displacement

rotations in the counterclockwise direction have what sign

Answer 9

positive

Question 10

angular velocity is a scalar or vector

Answer 10

vector

Question 11

angular acceleration is a scalar or vector

Answer 11

vector

Question 12

angular displacement

Answer 12

distance the point has traveled along the arc length

Question 13

the greater the radius of rotation, there is less/more LINEAR distance undergone by that point during angular motion

Answer 13

more linear distance traveled

Question 14

ex: swinging a baseball bat

describe angular + linear displacements of points near handle + end of bat

Answer 14

-points near handle + end of bat are moving the same ANGULAR displacement
-points near handle move less LINEAR displacement than points at end of bat

Question 15

ex: bike gearing

describe angular + linear displacements at different points of gear

Answer 15

-must have equal LINEAR displacements because connected by a chain
-ANGULAR displacement is different now

Question 16

tangential velocity

Answer 16

linear velocity at an instant in time
-must be tangent to curve

Question 17

what does radial acceleration cause

Answer 17

causes the change in direction of the linear/tangential velocity

Question 18

what is radial acceleration directed towards

Answer 18

center of rotation

Question 19

when is radial acceleration present

Answer 19

when angular velocity is non-zero
-doesn’t matter what angular acceleration is

Question 20

centripetal force

Answer 20

keeps body on a curve trajectory

Question 21

what does centripetal force cause

Answer 21

radial acceleration of the body in motion

Question 22

in the case of a bicyclist, what is the centripetal force

Answer 22

friction; it keeps bike from slipping during a turn

Question 23

tangential acceleration

Answer 23

-directed tanget to the curve
-perpendicular to the radial acceleration

Question 24

when is tangential acceleration present

Answer 24

when angular acceleration is non-zero

Question 25

describe angular acceleration of a figure skater doing revolutions

Answer 25

as their revolutions per second increase over time, they will have a non-zero angular acceleration, which produces linear tangential acceleration for a given point on their body

Question 26

total linear acceleration

Answer 26

the vector composition of the radial + tangential accelerations

Question 27

if an object is orbiting at a constant angular velocity is angular acceleration zero?

Answer 27

angular acceleration is zero

Question 28

if an object is orbiting at a constant angular velocity is linear acceleration zero?

Answer 28

linear acceleration is not zero because we have radial acceleration, which is a component of linear acceleration

Question 29

what happens if tangential acceleration + tangential velocity are in opposite directions

Answer 29

object is slowing down

Question 30

is it possible to have zero radial acceleration and non-zero tangential acceleration

Answer 30

-if you have zero radial acceleration, angular velocity must be zero
-you can still have non-zero tangential acceleration for a MOMENT IN TIME

Question 31

general motion involves…

Answer 31

combination of rotation + translation

Question 32

what is true of 2 connected bike gears of different size radii

-the angular displacement of the gears must be equal
-both the linear distance traveled by points A + B as well as the angular displacements of the gear must be equal
-the linear distance traveled of points A + B on their edges must be equal

Answer 32

the linear distance traveled of points A + B on their edges must be equal

Question 33

if someone changes their rotational direction which of the following are true about the moment of transition from rotating one way to the other way? (mark all that apply)

-radial acceleration is 0
-angular acceleration is 0
-angular velocity is 0
-tangential acceleration is 0

Answer 33

-radial acceleration is 0
-angular velocity is 0

Question 34

true/false: during mid single leg stance of walking gait the hip reaches its most extended angular position

Answer 34

false

Question 35

during the gait cycle the deepest knee flexion angle occurs during what phase/event of the gait cycle?

-absorption of momentum following heel strike
-initial contact (heel strike)
-early/mid swing
-mid stance
-instant toe off

Answer 35

early/mid swing

Question 36

true/false: when you use an angular to linear conversion equation (ex: v=rw) it is important to keep the sign (-/+) of the result because it tells you the direction of the resulting linear vector

Answer 36

false; the equations only give you the magnitude of the linear quantity

Question 37

true/false: the ankle is dorsiflexing (moving towards dorsiflexion) as the walker appraches mid swing

Answer 37

true

Question 38

when is the hip maximally flexed

Answer 38

from terminal swing to initial contact

Question 39

when does the hip reach max extension

Answer 39

at opposite initial contact

Question 40

when does the knee reach max extension

Answer 40

at heel rise

Question 41

when does the knee reach max flexion

Answer 41

during initial swing

Question 42

when does ankle reach max plantarflexion

Answer 42

right after toe off

Question 43

when does the ankle reach max dorsiflexion

Answer 43

during terminal stance + swing