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Biomechanics - Motion And Kinetics > Linear/Angular Kinetics > Flashcards

Linear/Angular Kinetics Flashcards

1
Q

What is a force?

A

Push or pull acting on the body

*vector

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2
Q

A vector has?

A

Magnitude
Direction
Point of application

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3
Q

How is a force represented?

A

Graphically by line of action/resultant

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4
Q

Forces are measured in

A

Newtons

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5
Q

… Newton is the force required to give a mass of …. Kg and acceleration of … m.s*2

A

1
1
1

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6
Q

Explain Newtons 1st law

A

THE LAW OF INERTIA: the state of a body will remain unchanged unless an external force is applied to it.

  • if a body possess mass then it also has intertia
  • so if a body is at rest it wants to stay that way
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7
Q

What is intertia?

A

The reluctance of a body to change its state

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8
Q

What is important to remember about inertia?

A

The force required to overcome intertia is proportional to the mass

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9
Q

What external forces are acting in the keg toss?

A

Air resistance

Gravity

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10
Q

Explain newtons 2nd law

A

THE LAW OF ACCELERATION: net force is equal to mass times acceleration
F = m X a

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11
Q

What happens if intertia is overcome?

A

The state of motion will change and we will have an acceleration - increasing or decreasing speed

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12
Q

SI unit of mass

A

Kilogram

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13
Q

SI unit of weight

A

Newton

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14
Q

Acceleration due to gravity

A

g= 9.81 m/s2

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15
Q

Explain newtons 3rd law

A

For every action there’s an equal and opposite reaction

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16
Q

What do we need to exert a force?

A

Friction

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17
Q

How do friction and newtons 3rd law relate?

A

When we apply a force to the ground:
The ground applies a force back on us
Add 2nd law and your body accelerates

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18
Q

3 external forces acting on the body

A

Friction
Impact
Gravitational

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19
Q

What are friction forces?

A

Oppose the relative motion or tendency of such motion of two surfaces in contact

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20
Q

What are impact forces?

A

Occur when two or more bodies collide

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21
Q

What are gravitational forces?

A

The force of attraction between masses

22
Q

3 examples of forces acting inside the body

A

Contact
Friction
Muscle

23
Q

What are contact forces?

A

Occur when 2 or more bodies are in contact

24
Q

What are muscle forces?

A

Forces caused by the contraction of muscles

25
Q

What are free body diagrams?

A

Include ALL of the external forces acting on a body

* if airborne and aerodynamic forces are neglected, this involves just the weight of the body

26
Q

Pressure equation

A

Area

27
Q

4 factors affecting GRF

A

Body mass
Speed
Type of foot strike/ gait surface
Footwear - reduced loading rates, cushioning

28
Q

What is a ground reaction force?

A

A force applied to the ground/floor is equally matched by the reaction force of the floor/ground.

  • all surfaces produce a reaction force
  • if you push against the ground, the ground pushes back with a force equal in magnitude but opposite in direction.
29
Q

How is GRF commonly measured?

A

Force platform

30
Q

How do you measure forces?

A

KISTLER
Mass 42kg
Accuracy 2% within 10-10,000N

31
Q

3 components of GRF

A

Fx
Fy
Fz

32
Q

How do you calculate magnitude?

A 
Resultant force (Fr)
= ¥ ( Fy2 + Fz2 )
33
Q

How do you calculate direction?

A

Angle to horizontal (@)
tan@ = opposite/ adjacent
tan@ = Fz/Fy = …….
@ = tan-1

34
Q

What is the moment of a force?

A

Defined by a force acting at a distance about an axis of rotation

35
Q

Moment of a force equation

A 
Moment = force x distance 
M            =  F      x     D
(N.m)      =  (N)    x     (m)
36
Q

What is a moment arm?

A

Exists between the joint axis (fulcrum) and muscle force (effort)

  • when a muscle contracts its pulls on its point of attachment along a line of action
37
Q

What is the moment of intertia?

A

Refers to the resistance of a body to change its state of angular motion
* intertia depends on objects mass

38
Q

Moment of intertia equation/unit

A

I = m. r2

(m= mass of segment/body, r= distance from axis of rotation)

kg.m2

39
Q

Explain forces at an instance in time

A

EF = m.a

If acceleration is zero= static analysis
If acceleration is non-zero = dynamic analysis

*when a body is completely MOTIONLESS, it is considered to be in a STATIC EQUILIBRIUM

40
Q

Dynamic analysis equations

A

E f Horizontal = m.a Horizontal
E f Vertical = m.a Vertical
E m 2 = 1 g A

41
Q

What are the 2 conditions for motion?

A
  1. The resultant force (Fr) is related to the acceleration of the object
  2. The resultant moment (Mr) is related to the angular acceleration of the object
42
Q

7 biomechanical principles that apply in the vertical jump

A 
Acceleration 
Velocity 
Displacement 
Time 
Newtons 2nd law 
Vertical force 
Newtons 3rd law
43
Q

Impulse equation

A

Force x time

44
Q

Define impulse

A

Determines the effect of a force applied to a body over a period of time
*the product of force and time and thus is represented by the area under the force-time curve

45
Q

What is graphical integration?

A

The process by which the area under the curve is found

46
Q

Method and implication of graphical integration

A

Counting squares

- time consuming/ prone to error

47
Q

What is the trapezium rule?

A

Assumes that over small time gaps, the area under the force-time curve approximates a trapezium

48
Q

Trapezium rule equation

A

1/2 x (f1 + f2) x T

* total area under curve = sum of each individual trapezium

49
Q

What is linear momentum?

A

A measure of the quantity of motion, taking into account both the mass of the body and its linear velocity

  • faster a body of a given mass moves - greater momentum
  • greater a body’s mass - larger momentum at given velocity
50
Q

Linear momentum equation/unit

A

M = m X v

  • kg. m.s-1
51
Q

What is the impulse-momentum relationship?

A

The impulse of a force is equal to the time rate of change in momentum

52
Q

Impulse-momentum equation

A 
F*t = mv - mu
F*t = m (v)

Biomechanics - Motion And Kinetics (3 decks)

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