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

Linear/Angular Kinetics Flashcards

(52 cards)

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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?

Study These Flashcards
A

The force of attraction between masses

22
Q

3 examples of forces acting inside the body

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A

Contact
Friction
Muscle

23
Q

What are contact forces?

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A

Occur when 2 or more bodies are in contact

24
Q

What are muscle forces?

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A

Forces caused by the contraction of muscles

25
What are free body diagrams?
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
Pressure equation
Force -------- Area
27
4 factors affecting GRF
Body mass Speed Type of foot strike/ gait surface Footwear - reduced loading rates, cushioning
28
What is a ground reaction force?
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
How is GRF commonly measured?
Force platform
30
How do you measure forces?
KISTLER Mass 42kg Accuracy 2% within 10-10,000N
31
3 components of GRF
Fx Fy Fz
32
How do you calculate magnitude?
``` Resultant force (Fr) = ¥ ( Fy2 + Fz2 ) ```
33
How do you calculate direction?
Angle to horizontal (@) tan@ = opposite/ adjacent tan@ = Fz/Fy = ....... @ = tan-1
34
What is the moment of a force?
Defined by a force acting at a distance about an axis of rotation
35
Moment of a force equation
``` Moment = force x distance M = F x D (N.m) = (N) x (m) ```
36
What is a moment arm?
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
What is the moment of intertia?
Refers to the resistance of a body to change its state of angular motion * intertia depends on objects mass
38
Moment of intertia equation/unit
I = m. r2 (m= mass of segment/body, r= distance from axis of rotation) kg.m2
39
Explain forces at an instance in time
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
Dynamic analysis equations
E f Horizontal = m.a Horizontal E f Vertical = m.a Vertical E m 2 = 1 g A
41
What are the 2 conditions for motion?
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
7 biomechanical principles that apply in the vertical jump
``` Acceleration Velocity Displacement Time Newtons 2nd law Vertical force Newtons 3rd law ```
43
Impulse equation
Force x time
44
Define impulse
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
What is graphical integration?
The process by which the area under the curve is found
46
Method and implication of graphical integration
Counting squares | - time consuming/ prone to error
47
What is the trapezium rule?
Assumes that over small time gaps, the area under the force-time curve approximates a trapezium
48
Trapezium rule equation
1/2 x (f1 + f2) x T | * total area under curve = sum of each individual trapezium
49
What is linear momentum?
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
Linear momentum equation/unit
M = m X v * kg. m.s-1
51
What is the impulse-momentum relationship?
The impulse of a force is equal to the time rate of change in momentum
52
Impulse-momentum equation
``` F*t = mv - mu F*t = m (v) ```

Biomechanics - Motion And Kinetics (3 decks)

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