LECTURE #18 - angular kinetics

Question 1

what does angular motion refer to ?

Answer 1

rotation about a point, and occurs when a force acts about a distance from a fixed point

Question 2

what is angular motion measured in ?

Answer 2

degrees or radians

Question 3

what does angular kinetics refer to ?

Answer 3

the branch of mechanics that deals with the causes of angular motion

Question 4

what is “centre of mass/gravity” ?

Answer 4

point around which mass or weight is considered to be concentrated (balance point of the body)

Question 5

what is the fulcrum ?

Answer 5

the support about which a lever turns

Question 6

what does the centre of mass serve as ?

Answer 6

an index of total body motion

Question 7

what might the centre of mass be in reference to ?

Answer 7

whole body or individual segments : % of body height and % body of segment length

Question 8

what does the location of the centre of mass determine ?

Answer 8

the way the body responds to external force

Question 9

what is the location of the century of gravity dependent on ?

Answer 9

the shape of the body

Question 10

TRUE OR FALSE

the centre of gravity moves as the body changes shape

Answer 10

TRUE

Question 11

whats the example in class we looked at as an example of the centre of gravity ? (video in class)

Answer 11

fosbury flop ted talk - pole vault

Question 12

how many ways are there to determine the centre of gravity ?

Answer 12

4

Question 13

what are the four ways to determine the centre of gravity ?

Answer 13

1) balance method
2) suspension method
3) MRI reconstruction
4) segmental method

Question 14

describe the balance method :

Answer 14

the weight (force of gravity) and vertical reaction force at the fulcrum (axis) must lie in the same plane

Question 15

describe the suspension method :

Answer 15

same principal as balance method but easier to accomplish

Question 16

describe the MRI reconstruction method :

Answer 16

using MRI as trunk segment contraction and scanning planes

Question 17

describe the segmental method :

Answer 17

• divide the body into connected rigid segments
• the CG and mass for each segment can be determined experimentally (MRI or cadavers)
  the total body CG is then computed from the segmental information

Question 18

what are some limitations and assumptions in regards to determining the centre of gravity ?

Answer 18

• based on white male cadavers
• completed in the 1930s-40s (bodies have changed; taller and larger people nowadays)
• based on segment being “truncated cones”

Question 19

TRUE OR FALSE

equilibrium and stability are the same thing

Answer 19

FALSE
equilibrium and stability are not the same thing

Question 20

what is biomechanics stability ?

Answer 20

stability of a loaded structure to maintain static equilibrium

Question 21

how is biomechanical stability maintained ?

Answer 21

as long as the vertical projection of the centre of gravity remain within the base of sport

Question 22

what is mechanical stability ?

Answer 22

the ability to maintain vertical projection of CG within the base of support

Question 23

FILL IN THE BLANK

When other factors remain constant, a body’s ability to maintain stability is increased by increasing its mass or by ________________

Answer 23

When other factors remain constant, a body’s ability to maintain stability is increased by increasing its mass or by WIDENING ITS BASE OF SUPPORT

Question 24

what are some factors that play a role in a body’s ability to maintain stability :

Answer 24

1) increased mass
2) increased function between body and surface
3) increased size of the base of support
4) positing the centre of gravity as low as possible in vertical direction
5) positioning the centre of gravity close to edge of the base of support in direction of the oncoming external force

Question 25

TRUE OR FALSE

as people age, they become less stable and gain decreased proprioceptive ability ?

Answer 25

TRUE