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SPS1502 - biomechanics > exam study deck > Flashcards

exam study deck Flashcards

1
Q

what are four characteristics of a closed kinetic chain exercise

A
  1. both ends of the chain are fixed
  2. no part of the chain can move independently to each other
  3. movement at the most proximal link can theoretically result in a completed movement
  4. usually push-like movement pattern
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2
Q

what is the consequence of a push-like movement pattern

A

movement speed is limited by the speed of the muscle shortening

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3
Q

What are the two mechanisms of a throw like pattern

A
  1. transfer of angular momentum
  2. storage and release of elastic energy
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4
Q

describe mechanism 1 of a throw like pattern

A

large muscles moving proximal segments can induce large momentum into the chain systems

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5
Q

define radius of gyration

A

distribution of mass with respect to a given axis of rotation

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6
Q

describe mechanism 2 of a throw like movement pattern

A

high speed movements also result from elastic recoil tendons

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7
Q

what is the difference between radius of gyration and centre of gravity

A

radius of gyration changes as the point of rotation changes where centre of gravity does not

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8
Q

when should a throw like pattern be used

A

when the shot is relatively light and distance/ speed is the key goal

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8
Q

what is a throw like movement

A

any movement where proximal segments accelerate distal segment by transfer of momentum

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9
Q

when should a push-like pattern be used

A

when the shot is relatively heavy and force is the key goal

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10
Q

what is an open kinetic chain

A

one end of the chain is fixed and the other is free to move

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11
Q

what is a closed kinetic chain

A

chain where both ends are fixed

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12
Q

mono-articular muscle

A

muscle that crosses one joint

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13
Q

bi-articular muscle

A

muscle that crosses two or more joints

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14
Q

when are bi-articular muscles useful

A
  1. when two simultaneous movements are performed concurrently
  2. redistribution of muscle torque/power
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15
Q

mechanical work

A

product of force and displacement

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16
Q

kinetic energy

A

energy of movement

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17
Q

thermal energy

A

average kinetic energy of the molecules in the object

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18
Q

elasticity

A

tendency to return to shape after distortion

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19
Q

compliance

A

tendency to be deformed when a force is applied

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20
Q

stiffness

A

inverse of compliance

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21
Q

can the total energy in a system change?

A

no

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22
Q

friction

A

force at the interface of 2 surfaces

23
Q

what occurs if the object is stationary

A

forces of friction is equal to the sum of all forces that would produce motion

24
Q

what occurs if the object is moving

A

forces of friction is less than the sum of all forces that would produce motion

25
Q

rolling friction

A

friction that resists the rolling on an object

26
Q

what is rolling friction caused by

A

deformation at surfaces that oppose the motion

27
Q

what is the difference between friction and traction

A

friction is the movement of one surface over another whereas traction is the physical act of pulling something along a surface, using motive power

28
Q

describe the two factors that affect friction

A
  1. normal reaction force (R) - if greater forces pressing two surfaces together, there is more friction
  2. coefficient of friction (u) - surfaces of characteristics - quality of bonds formed
29
Q

how does a sports scientist test for friction

A
  1. using a spring scale to measure the force required to move or continue to move an object across a surface
  2. use a force platform to measure the force under specific conditions
30
Q

where is the info around friction used

A
  1. design of netball, hiking, running shoes
  2. design of playing surfaces
  3. motor racing tyres
  4. engineering of testing equipment, resistance training machine
  5. bat/club faces, shoe surfaces, racquet strings
31
Q

what is the conservation of momentum (P)

A

total momentum, in any direction remains constant unless acted upon by an external force

32
Q

how is the conservation of momentum described mathematically

A

m1v1 = m2v2

33
Q

restitution

A

tendency for an object to return to the original shape after deformation

34
Q

coefficient of restitution

A

proportion of energy remaining after collision

35
Q

describe Newton’s Law of impact

A

if 2 bodies move towards each other along the straight line, the difference between their velocities immediately after the impact bears a constant relationship to the difference between their velocities at impact

36
Q

what are the effects on CoR

A
  1. Temperature - increased temperature = increased CoR
  2. impact velocity - increased velocity = decreased CoR
37
Q

what are the factors affecting a collision outcome

A
  1. increased mass of bat
  2. increased velocity of bat
  3. decreased mass of ball
  4. increased velocity of ball
  5. increased angle or incidence
  6. increased coefficient of restitution
38
Q

where can information about CoR be used

A
  1. properties of surfaces
  2. manipulation of objects
39
Q

fluid

A

any substance that continually flows or deforms

40
Q

laminar flow

A

smooth parallel layers of fluid

41
Q

turbulent flow

A

mixing adjacent fluid layers; change in fluid viscosity can occur if kinetic energy is taken from an object or surrounding

42
Q

what affects form drag

A

form of an object, frontal surface area, velocity

43
Q

surface drag

A

fluid particles adjacent to surface slowed because of shear stress

44
Q

boundary layer

A

area of affected particles

45
Q

how can surface area be reduced

A
  1. reducing fluid catching projections on an object’s surface
  2. decrease surface area in contact with fluid
  3. decrease velocity
46
Q

Bernoulli’s principle

A

region of relative high velocity flows are associated with regions of relative low pressure, the opposite is true fir regions of low velocity flows

47
Q

Lift: Bernoulli’s perspective

A

faster move over wing causes decreased pressure than under wing which results in lift force

48
Q

Lift: Newton’s perspective

A

decrease momentum of air required increased momentum of another mass; conservation of momentum of action - reaction

49
Q

what is the benefit of a ‘torpedo pass’ in rugby

A

a. keep the ball’s longnitudinal axis aligned with trajectory to minimise drag and increase range/ speed
b. decreased turbulence by decreasing fluid separation
c. need to spin the ball to maintain stability in flight

50
Q

hydrodynamics

A

fluid dynamics concerned with liquid

51
Q

buoyancy

A

upward, or lift forces exerted on an object by fluid

52
Q

archimedes principle

A

buoyancy force = weight of fluid displaced

53
Q

wave drag

A

drag acting on the interface of 2 fluids

54
Q

what methods can be used to minimise wave drag

A
  1. minimise up and down motion
  2. keep lead arm outstretched for longer
  3. keep head down, body lower in water = streamlined shape
  4. small amplitude flutter kicks
  5. minimise skin and form drag so that the water isn’t pushed in front of swimmer
55
Q

how do we produce backwards force

A

if we push our hand/arm backwards, a drag force will work in the opposite direction

56
Q

how do we increase drag

A
  1. increase relative velocity
  2. increase surface area
  3. increase coefficient of drag

SPS1502 - biomechanics (3 decks)

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