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Biomechanics > Biomechanics Exam 2 > Flashcards

Biomechanics Exam 2 Flashcards

1
Q

What do force plates do?

A

Measure three orthogonal reaction forces, Fx, Fy, Fz and three moments about these orthogonal axes, Mx, My, and Mz.

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2
Q

How do force plates measure force?

A

Through transducers sandwiched between rigid plates that convert force into voltage.

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3
Q

Ground Force Reaction

A

The reaction force provided by the support surface on which the movement is performed.

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4
Q

Calculate the resultant of the 3 reaction force vectors

A

Square root of the sum of the component forces squared

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5
Q

GRF Angles

A

Theta yz = inversetan(Fy/Fz)
Theta xz = inversetan(Fx/Fz)
Theta xy = inversetan(Fx/Fy)

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6
Q

Center of Pressure

A

Point on the force plate that the resultant force originates

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7
Q

COP(x)

A

My/Fz

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8
Q

COP(y)

A

Mx/Fz

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9
Q

Newton’s 1st Law

A

A body continues in its state of rest or uniform motion in a straight line unless compelled to change the state by external forces exerted upon it. Due to mass or inertia.

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10
Q

Inertia

A

property of a body to resist a change in its state of motion.

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11
Q

Moment of Inertia

A

Sum of m*r^2

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12
Q

Angular Momentum

A

Moment of inertia * Angular velocity

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13
Q

Newton’s 2nd Law

A

An unbalanced force applied to a body causes acceleration of that body (sum of the forces equals mass times acceleration)

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14
Q

Newton’s 2nd Law - Angular Acceleration

A

Sum of the torque equals Inertia time angular acceleration

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15
Q

Torque

A

Radius cross the force

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16
Q

Newton’s 3rd Law

A

For every action there is an equal and opposite reaction (torque and/or force)
Forces always come in pairs

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17
Q

Momentum

A

mass times velocity

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18
Q

Elastic collisions

A

objects rebound

19
Q

Inelastic collisions

A

object stick together and usually become distorted and generate heat.

20
Q

Coefficient of Restitution

A

describes the relative elasticity of an impact
perfectly elastic e = 1
inelastic e = 0
e = velocity after / velocity before

21
Q

Kinetic Energy

A

(1/2) m*v^2

22
Q

Power

A

Force * velocity

23
Q

1 hp

A

550 ft lbs / s = 746 W

24
Q

Potential Energy

A

mgh

25
Q

Motor Units

A

motor neuron and muscle fibers it innervates

26
Q

Fine control

A

small motor units contain as few as 20 muscle fibers per nerve fiber

27
Q

Strength control

A

a large number of muscle fibers per nerve fiber

28
Q

Erector Spiane Muscle

A

extends down the back, responsible for maintaining back posture in any “sitting” position.

29
Q

Basic strategies to prevent overexertion injury?

A

Design, select, train

30
Q

Recommended Weight Limit

(RWL) Equation

A

LCHMVMDMAMFMCM

31
Q

Lift Index (LI)

A

Task Load / RWL

32
Q

What does Lift Index (LI) mean?

A

LI < 1 - lifting task is safe for most workers

LI > 3 - many workers are at elevated risk

33
Q

Load Constant (LC)

A

max recommended weight for lifting at standard 23 kg or 51 lbs

34
Q

Horizontal Multiplier (HM)

A

HM (metric) = 25/H
HM (english) = 10/H
H = horizontal distance from hands to midpoint

35
Q

Velocity Multiplier (VM)

A

VM = (1-0.003 (V-75)) (cm)
VM = (1-0.0075 (V-30)) (in)
V is vertical distance of hands from floor

36
Q

Distance Multiplier (DM)

A

D is total vertical distance moved between origin and destination

37
Q

Asymmetric Multiplier (AM)

A

A is angle of symmetry (angular displacement in sagittal plane)

38
Q

Frequency Multiplier (FM)

A

based on work duration and V (vertical distance from floor)

39
Q

Coupling Multiplier (CM)

A

based on V (vertical distance of hands from floor in cm) and quality of coupling

40
Q

Area under a force distance curve is ____ .

A

Work

41
Q

Units associated with impulse are ____ .

A

Newtons * sec

42
Q

Torque is angular acceleration * ____ .

A

Inertia

43
Q

Angular velocity * Inertia

A

Angular Momentum

44
Q

Which multiplier in the NIOSH lifting equation has the most influence on determining the safety of a given task?

A

HM (Horizontal Multiplier)

Biomechanics (1 decks)

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