Biomechanics Exam 3

Exam is Wednesday, December 3

moment of inertia 

Inertial resistance for an angular system is dependent on _____.

mass of object

Inertial resistance for an linear system is dependent on _____.

slope

Resistance to F(gravity) is dependent on _____.

Coefficient of friction

_____ is a variable that represents the shared resistance between two surfaces.

less

Friction resistance is ______ if the slope is 10 degrees compared to a horizontal surface.

lubrication, decreasing mass, and increasing slope

Friction resistance can be reduced by _____.

decreases

Friction resistance _____ acceleration.

moment of inertia and rolling resistance

The two types of resistance exclusively affecting wheels are _____.

v²

Air resistance is proportional to _____.

form and skin

Air resistance is affected by the shape and flow around an object. This is referred to as _____ drag.

joint friction, muscle tissue, and CNS control

Sources of internal resistance to movement include:

the force that opposes the initial movement between two surfaces that are in contact and at rest.

Static friction is ______.

the force that opposes the relative motion between two surfaces sliding past each other.

Kinetic friction is _____. 

Contact force between the object and the support surface (i.e., vertical force) and the coefficient of friction (C(friction)) between the object and the support surface

Friction is dependent on _______.

parasitic drag

Typical air resistance is referred to as _____.

To calculate complex motion performance under real-life conditions

What is the main purpose of a performance equation in biomechanics?

Power

Which physical quantity is most commonly evaluated using the performance equation for biking and rowing?

Gravity

Which force acts as propulsion in downhill skiing according to the performance equation?

Efficiency of the system

What does 'eff' represent in the performance equation?

Exponential

In the performance equation, what type of relationship does aerodynamic drag have with velocity?

Biking

Which sport typically has the highest mechanical efficiency?

Performance equations use resistive forces

What is the key difference between using the performance equation versus uniformly accelerated motion (UAM) equations?

Mass

Which component contributes to rolling resistance in biking?

Watts can be positive or negative

What problem arises in skiing when solving for velocity using the performance equation?

Difficulty collecting accurate real-time data

What challenge is commonly encountered when applying performance equations to real-life activities?

Fulcrum, applied force, and load

What are the three contact points that define a lever system?

Tennis shoe sole

Which of the following is NOT an example of a lever used in sports?

Ratio of output force to input force

What does mechanical advantage (MA) of force represent in a lever?

1st class lever

Which lever class provides both force and velocity mechanical advantages?

F1 x d1 = F2 x d2

What is the formula used to express torque balance in levers?

3rd class lever

Which lever class is typically used to generate high speed at the expense of force?

Displacement

In terms of mechanical advantage, what increases when leverage force decreases?

3rd class

What class lever is the elbow?

Torque clockwise equals torque counterclockwise

What happens in a torque balance scenario?

Balancing weights on a beam

Which of the following combinations is most likely to use torque balance in biomechanics?

Force advantage (leverage)

ratio of output force to input force

Velocity advantage (speed)

ratio of distance (force) to distance (load)

Second class lever

Which lever positions the load between the fulcrum and the effort

joint compression force

When the arm is abducted into the horizontal position, contraction of the deltoid muscles causes an increase in _____.

axis of rotation

When the shoulder is externally rotated, the humerus rotates along the _____.

almost 0

Consider performing an isometric bicep curl where your humerus is vertical and your forearm is horizontal. When the elbow is flexed at 90 degrees, the compressive force on the elbow joint is _____.

line of force

In the formula for torque, F*r, r is the distance from the axis of rotation to the _____. 

all

When you jump off of a curb and land on the ground, _____ muscles contract.

head of the trochanter

In older adults, increased vertical forces acting on the hip increase fracture risk of the _____.

patella

When the quadriceps contract, the _____ provides compressive force that stabilizes the knee.

valgus, varus

In the accompanying figure, the knee alignment is considered to be excessive _____ and the ankle alignment is excessive _____.

motion segment

Two adjacent vertebrae and the associated soft tissue is called a _____.

pulposus

The part of the intervertebral disc that acts as the fulcrum for spinal bending is the _____.

Inertia

Resistive force proportional to mass

Slope

Angle of inclination

Gradient

Another term for slope or inclination

Agonist

Muscle responsible for the primary movement

Antagonist

Muscle that opposes the primary movement

Synergists

Provide secondary movement control and stability

power, locomotion, shock absorption, balance/stability

The primary functions of the lower extremities include _____.

What are the major loads acting on the hip during stance?

The weight of body segments above the hip (wt) the tension in the hip abductor muscles (Fm) and the joint reaction force (R) generated in accordance with Newton’s 3rd law

Varus

An inward angulation of the distal segment of a bone or joint

Valgus

Refers to an outward angulation of the distal segment of a bone or joint

Intervertebral Discs

fibrocartilaginous structures that cushion spinal joints

Shear forces 

sliding forces perpendicular to the normal force

20

What percentage of the gait cycle is spent in the double support phase? (Remember you have two legs)

At mid-stance

In the walking gait cycle, when does the center of mass reach its highest point?

heel strike to toe-off

The double stance phase of gait is from _____ to  _____.

Braking and propulsion

What does the ground reaction force in the sagittal plane primarily reflect?

Conservation of energy

Pendulum motion during the gait cycle uses which concept of biomechanics?

GAITRite

Which clinical tool is used to measure gait performance over a fixed distance?

Overground provides more natural visual feedback

What is the key difference between overground and treadmill gait assessment?

running only

The spring-pendulum model for gait applies to _____.

Decreased flexion

What would change in knee joint range of motion due to increased joint stiffness?

center of mass/center of pressure alignment

Treadmill walking alters _____.