WEEK 8 Flashcards
(22 cards)
define mechanical work and what is its equation
the product of the component of force acting in the direction of the displacement and magnitude
work= force x displacement ( newton metres or joules)
what is an isotonic contraction (concentric/ eccentric)
muscle that shortens or elongates
define an isometric contraction
no change in muscle length
what is a concentric contractions work and what direction does it go in
positive work
next muscular force and movement are in the same direction
what is an eccentric contractions work and what direction is it in
negative work
net muscular force and movement are in opposite directions
describe the work of an isometric contraction
no work
no displacement , because no muscle change is occurring
define power and describe its equation
def= the amount of mechanical work performed in a period of time.
( if you can move something quickly that is heavy= powerful)
Power= work divided by time
power= force x velocity ( joules per second or watts)
define kinetic energy and describe the equation
def= energy due to the motion of an object
100% contributions to all energy
KE= 1/2 x mv ^2 (do the squared first)
define gravitational potential energy and what is its calculation
def= energy due to the position (height) of an object
mass x gravity x height (how high we are off the ground. )
define strain energy and its equation
a special form of potential energy
SE= 1/2 Kx ^2
describe the work and energy relationship
work causes changes in the mechanical energy of a system.
W= mechanical energy= potential energy
describe mechanical work versus energy expenditure
mechanical energy= work divided by energy expenditure x 100%= work output divided by work input
define the centre of gravity (x2)
1- the point at which the body’s mass is evenly distributed. the weight of the body is balanced in all directions (centre of mass)
2- the point about which the sum of torques produced by each body segment is equal to zero.
describe the centre of gravity location
- when standing your centre of gravity is located approx 55-57 % of your standing height
describe changing the centre of gravity position (x2)
- re orienting the limbs to shift centre of gravity
- shift magnitude relative to limb mass and position
changing centre of gravity position (high jump and gymnastics )
high jump = centre of gravity follows a parabolic path, passing below the bar
dance gymnastics = centre of gravity follows a parabolic path, But the head remains at the same level.
what are the 3 steps to calculating centre of gravity in the body and describe each
1) balance of the board
2) reaction board (sum of torques= 0)
3) segmental method
- accounts for segment masses and centre of gravity locations
- calculates the total body centre of gravity based on these
- represents segment torques about the reference point.
describe the calculations for the segmental centre of gravity method
- calculate the sum of the segment torques about your axis of rotation
- divide by the total body mass
define stability and balance
the resistance to both linear and angular acceleration or the resistance to the disruption of equilibrium
what are the 5 mechanical factors that affect stability and balance
1) according to newtons law of motion, the more massive an object is the greater the force required to produce acceleration
2) the size of the base of support
3) horizontal location of the centre of gravity relative to the base of support
4) vertical location of the centre of gravity relative to the base of support
5) friction between the two surfaces
define gait/running
often described as a series of controlled falls
badminton example with stability and balance with badminton eg
offensive= if you know where you are going you can be high and unstable
defensive= if you don’t know where you are going you need to be low and stable
