LECTURE #18 - angular kinetics Flashcards
what does angular motion refer to ?
rotation about a point, and occurs when a force acts about a distance from a fixed point
what is angular motion measured in ?
degrees or radians
what does angular kinetics refer to ?
the branch of mechanics that deals with the causes of angular motion
what is “centre of mass/gravity” ?
point around which mass or weight is considered to be concentrated (balance point of the body)
what is the fulcrum ?
the support about which a lever turns
what does the centre of mass serve as ?
an index of total body motion
what might the centre of mass be in reference to ?
whole body or individual segments : % of body height and % body of segment length
what does the location of the centre of mass determine ?
the way the body responds to external force
what is the location of the century of gravity dependent on ?
the shape of the body
TRUE OR FALSE
the centre of gravity moves as the body changes shape
TRUE
whats the example in class we looked at as an example of the centre of gravity ? (video in class)
fosbury flop ted talk - pole vault
how many ways are there to determine the centre of gravity ?
4
what are the four ways to determine the centre of gravity ?
1) balance method
2) suspension method
3) MRI reconstruction
4) segmental method
describe the balance method :
the weight (force of gravity) and vertical reaction force at the fulcrum (axis) must lie in the same plane
describe the suspension method :
same principal as balance method but easier to accomplish
describe the MRI reconstruction method :
using MRI as trunk segment contraction and scanning planes
describe the segmental method :
- 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
what are some limitations and assumptions in regards to determining the centre of gravity ?
- based on white male cadavers
- completed in the 1930s-40s (bodies have changed; taller and larger people nowadays)
- based on segment being “truncated cones”
TRUE OR FALSE
equilibrium and stability are the same thing
FALSE
equilibrium and stability are not the same thing
what is biomechanics stability ?
stability of a loaded structure to maintain static equilibrium
how is biomechanical stability maintained ?
as long as the vertical projection of the centre of gravity remain within the base of sport
what is mechanical stability ?
the ability to maintain vertical projection of CG within the base of support
FILL IN THE BLANK
When other factors remain constant, a body’s ability to maintain stability is increased by increasing its mass or by ________________
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
what are some factors that play a role in a body’s ability to maintain stability :
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
