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Year 12 Pe > Biomechanics > Flashcards

Biomechanics Flashcards

1
Q

What things affect how levers work

A

Length of lever, inertia of lever, amount of force applied

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2
Q

What’s newtons 1st law

A

(Inertia) An object will remain at a constant velocity unless acted upon by an external, unbalanced force

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3
Q

What’s newtons 2nd Law

A

(Acceleration) acceleration is directly proportional to the force applied and inversely proportional to the objects mass. F=ma, a= F/m

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4
Q

What’s newtons 3rd law

A

Every action has an equal and opposite reaction

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5
Q

What is the force motion principle

A

If force is applied to an object, motion will occur

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6
Q

What’s friction

A

The resistance that objects encounter when moving over another

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7
Q

What’s static friction

A

Force keeping objects at rest

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8
Q

What’s kinetic friction

A

Force that opposes movements

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9
Q

What’s inertia

A

An objects resistance to a change in its motion. Greater inertia = more force required to change its state of motion

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10
Q

What’s momentum

A

The quantity of motion of a moving body

P=mv

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11
Q

What’s impulse

A

change of momentum

I=Ft

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12
Q

What’s the impulse-momentum relationship

A

the impulse applied to an object will be directly proportional to the change in its momentum

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13
Q

What’s the law of conservation of momentum

A

The total momentum of two colliding objects will remain the same after the collision.

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14
Q

What are the types of collision

A

Perfectly elastic - all ‘p’ is conserved
Imperfectly elastic - some p lost
Perfectly inelastic - all p is lost

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15
Q

What’s coefficient of restitution

A

A measure of elasticity between two objects. 0-1 where 0 is perfectly inelastic collision and 1 is perfectly elastic

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16
Q

Example of perfectly elastic collision

A

Ball bouncing back to the exact drop height

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17
Q

Perfectly inelastic

A

Ball is dropped but there is no rebound

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18
Q

Imperfectly elastic collision

A

Ball bouncing lower than drop height

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19
Q

How to work out COR:

A

FV of one object - FV of other ➗ IV of other - IV of one object

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20
Q

Things that affect coefficient of restitution

A
  • equipment & materials
  • temp of materials (^temp=^COR)
  • velocity of collision (^v = decrease COR)
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21
Q

What’s a concentric force

A

A force applied directly through an objects centre of mass, resulting in translation

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22
Q

Example of concentric force

A

Pushing the puck in ice hockey

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23
Q

What’s Eccentric force

A

Force applied to an object offset from its centre of mass resulting in translation and rotation

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24
Q

Example of eccentric force

A
  • Tipping a waterbottle over by pushing the top

- tackle in AFL

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25
Q

What’s a force couple

A

When two equal but oppositely directed forces act on opposite sides of an axis of rotation at an equal radius, resulting in rotation of the object in a fixed position

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26
Q

What’s an example of a force couple

A
  • bike pedals to move around

- steering wheel

27
Q

What is Torque

A

A rotational force, resulting in angular motion

- T = F x radius (from axis)

28
Q

What is a moment arm

A

The distance from force application to the axis of rotation

29
Q

What happens when you change the length of the moment arm

A

Increase moment arm creates more torque but with the same amount of force exerted and vice versa

30
Q

How to create more torque

A

Increase force and/or radius

T = Fr

31
Q

What’s angular motion

A

The motion of an object about a relatively fixed axis

32
Q

What’s angular velocity

A

(w) - rate of change in angular displacement

33
Q

What’s angular acceleration

A

(a) rate of change in angular velocity over time

34
Q

What’s moment of inertia

A

And objects resistance to a change in its angular motion. Dependent on distribution of mass and mass itself
moi = mass x radius of rotation^2

Inertia is related to radius

35
Q

What’s angular momentum

A

(L) the quantity of angular motion possessed by a rotating body

L = moi x w

36
Q

What’s a mechanical advantage (lever)

A

Force arm longer than resistance arm

37
Q

What’s a speed advantage

A

Resistance arm longer than force arm

38
Q

What’s a first class lever

A

(RAF)

  • the further force is applied from the axis, the less force is needed to lift the resistance
  • C1 vertebrae
39
Q

Second class lever

A

ARF

  • longer force arm than resistance arm (mechanical advantage)
  • standing on tip toes
40
Q

Third class lever

A

AFR

  • force arm shorter than resistance arm (speed advantage)
  • arm
41
Q

What is Bernoulli’s principle

A

Increased velocity of fluid results in a decrease in pressure

42
Q

What is lift

A

The force that a fluid imparts on an object as it flows over it, that is perpendicular to the oncoming flow direction

43
Q

How is lift created

A

Fluid flowing over top of an object has to flow faster than fluid flowing over the bottom to reach the end at the same time. Pressure difference cause by Bernoulli’s principle causes fluid flow from high pressure to low pressure (up) and causes object to have lift

44
Q

What’s laminar flow

A

Fluid flowing in parallel layers with no disruption, at the same velocity and pressure

45
Q

What’s turbulent flow

A

Fluid flowing with irregular fluctuations, appearing random and at different velocities and pressure.

46
Q

How does flow affect boundary layer

A

Laminar- creates less surface drag, early separation point

Turbulent- creates more surface drag, late separation point

47
Q

What’s drag

A

A force that acts to oppose the motion of an object through fluid

48
Q

Total drag

A

Pressure drag + surface drag + wave drag

49
Q

What’s pressure drag

A

Force creates via pressure difference between the front and back of an object moving through fluid

50
Q

How is pressure drag created

A

Size of Low pressure region behind object (turbulent wake) determines size of pressure difference. Fluid flows from high to low pressure - Bernoulli’s principle - and slows down object.
^frontal cross sectional area = ^ pressure drag

51
Q

What’s surface drag

A

Drag caused by friction between the surface and the fluid flowing over it. A rougher surface traps more fluid and creates more friction

52
Q

What is wave drag

A

Drag created by the movement of water and generation of waves at the surface of water, occurring as a loss of energy from the creator.

53
Q

How to reduce wave drag

A

Decrease interaction with the surface. Either increase buoyancy, Change technique or go deeper.

54
Q

How can wave drag be advantageous vs disadvantaged

A

Adv- create waves behind, propelling forward

Disadv. - pushes water forward creating resistance

55
Q

What is buoyancy

A

An upward force exerted by a fluid that opposes the weight of the immersed body.
Affected by: - density of body in comparison to fluid
- volume of fluid displaced

56
Q

Factors affecting drag

A
  • Size of frontal cross sectional area
  • velocity and resulting pressure of object
  • texture of surface
  • Direction of fluid flow
  • size of wake
  • shape of object
  • slipstreaming
  • fluid viscosity
57
Q

Environmental factors affecting drag

A
  • altitude - ⬆️ altitude = ⬇️drag
  • humidity- ⬆️humidity = ⬇️drag
  • temperature - ⬆️temp of fluid = ⬇️ viscosity = ⬇️ drag
58
Q

What’s the Magnus effect

A

The way an objects path through fluid is changed due to spin, occurring perpendicular to fluid flow through the axis of rotation

59
Q

How does spin affect flight paths

A

Backspin- stays in the air longer
Topspin- stays in the air less
Sidespin - travels side to side

60
Q

What’s not Magnus

A

Anything that doesn’t spin

Eg. Swing (cricket), knuckleball, float serve

61
Q

Top spin rebound

A

Moves fast, kicks on, travels further after bounce

62
Q

Back spin rebound

A

Bounces high, slows down, travels less distance after bounce

63
Q

What’s buoyancy affected by

A
  • Density of body in comparison to fluid

- volume of fluid displaced

Year 12 Pe (4 decks)

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