Biomechanics
The phenomenon where range of a movement is limited due to the tightness of structures on the other side of a segment is known as..
passive insufficiency
A person using an elastic resistance band with a spring constant of 74, pulls the band from a length of 1.3m to a length of 2.8m. If the person has a mass of 85kg and holds the band stretched for 10 seconds, how much strain energy is stored in the band when it is stretched?
83.3 joules
An 87kg person lands on a 100kg trampoline with a spring constant of 2600. If the person stretches the trampoline 0.8m over a period of 0.3 seconds, what is the stored strain energy when the trampoline is fully stretched?
832 joules
The fields of "kinetics" and "kinematics" both fall under the field of "statics".
False
The order in which someone uses either step length or cadence to increase their overall gait velocity changes depending on whether they are walking or running.
False
There is only one sagittal plane and it cuts the body perfectly into left and right halves. You cannot cut a sagittal plane on either side of the mid-line.
False
Torque: When a static pose is maintained (i.e. there is no movement), one can assume that the net torque acting on the joints is zero.
False
We are studying rigid-body mechanics in this course because the human body is not deformable
False
When a person wants to increase their walking speed, they first increase their cadence, and then if they want to walk faster than that they will increase their stride length.
False
When we say that the skeleton is bilaterally symmetrical, we can also assume that the internal organs in those regions are bilaterally symmetrical.
False
Which of the following does not occur during a walking gait cycle?
Flight phase
A human gait cycle begins when which of the following gait events occurs?
Foot Contact
What structures must be formed when the muscle is stimulated in order for force to be generated?
cross-bridges
Another name for a transverse plane is a
cross-section
A baseball flying in an arc is best described as which type of motion?
curvilinear motion
To fully define a vector quantity, you must specify
direction and magnitude
Which of the following best explains why performing one full repetition of a bench press is an example of doing NO net mechanical work to the bar?
displacement = 0
In a 5 kilometer road race, the finish line is also the starting line. What does 5 kilometers represent?
distance
A track and field discus thrower releases a discus from the edge causing the discus to spin/rotate as it flies through the air. This confirms that at least one force applied to the discus is
eccentric
What type of muscle contraction is required of your biceps when you lower your backpack to your desk in a slow, controlled manner?
eccentric
What type of muscular contraction is associated with negative mechanical work?
eccentric
When catching a ball, such as a medicine ball, your shoulders will horizontally abduct and your elbows will flex resulting in your pectoralis major and triceps...
ecentrically contracting
"Distance" and "displacement" are the exact same thing.
false
Biomechanics is a field of study ONLY involving the movement and forces associated with human beings.
false
During the up-phase of a traditional sit-up exercise your lower back muscles (erector spinae) are lengthening and therefore they must be actively eccentrically contracting.
false
Getting up out of a chair (from sitting posture to standing posture) typically involves eccentric contractions of your lower extremity muscles.
false
Internal forces that "push" on the ends of bones are tensile forces.
false
Linear Kinetics: Although momentum includes velocity which can be positive or negative, momentum is always positive
false
Mechanical Work: Running downhill would likely result in the quadriceps doing more positive work due to the increased knee flexion.
false
Muscle Mechanics: Muscles tend to generate the most force when they are shortened because there is maximum actin-myosin overlap.
false
Negative work is associated with isometric contractions
false
Negative work is associated with isometric contractions.
false
The passive tension that a muscle is capable of generating comes from the actin and myosin.
false
The study of rigid body mechanics allows us to study the deformation of an object.
false
n most throwing situations, we can also add mass to an object when we're trying to increase its momentum. For example, baseball pitchers often do this during a game.
false
the formula for mechanical work is the product of which of the following?
force and displacement
Which of the following does NOT indicate that an object has accelerated?
if the object maintains constant velocity
Which of the following represents a non-contact force?
magnetic force
Where something is located in space is known as its...
position
EMG is an analytical technique that directly measures which of the following?
motor unit action potentials
The internal torques that are generated from WITHIN the body, almost always come from..
muscles
Which of the following would NOT be measured in a "kinematic" analysis of a tennis serve?
muscular force
Which of the following is NOT known to negatively impact someone's balance?
muscular hypertrophy
Which structure within the sarcomere generates the pulling force?
myosin
When initial velocity is more positive than final velocity, the acceleration is what?
negative
Which of Newton's laws explains the observation of normal contact, or ground reaction, forces?
newtons law of action-reaction
Which of the following is NOT one of Newton's three law of motion?
newtons law of gravity
Which of Newton's laws explains that an object will either continue to move, or remain at rest, based upon the amount of mass contained within the object?
newtons law of inertia
Which of the following is the correct unit of measure for torque?
nm
During a gymnastics routine, a gymnast on the rings holds a pose perfectly still for five (5) seconds while exerting a force of 135N. Which type of work was the gymnast doing in this example?
no work
A football player pushes a sled with a force of 1000N over a single trial that spans 40 yards. Which of the following CANNOT be calculated from this information?
none of the variables in this list can be calculated
The measure of the total length of the path followed by an object from its starting position to its ending position is known as
not displacement
What is the term that best describes the amount of distance that an object travels compared to its overall displacement (i.e. distance/displacement = )?
not entropy
Surface EMG allows a clinician to record the electrical impulses that...
occur within a given pick-up area
A boulder resting on top of a mountain has a lot of...
potential energy
Mechanical Energy: A boulder resting on top of a mountain has a lot of..
potential energy
Mechanical Energy: The capacity for doing work that a body possesses because of its weight and height, or position, is called what?
potential energy
All of the following are terms for the benefits of biomechanics in the workplace, EXCEPT
recreational biomechanics
A hockey puck sliding in a straight line across an ice rink is best described as which type of motion?
rectilinear motion
A marble sinking straight down in water is best described as which type of motion?
rectilinear motion
The sum of all forces acting on an object is the..
resultant force
Which of the following types of motion is another name for "angular motion"?
rotation
This cardinal plane cuts the body into right and left halves.
sagittal plane
Muscles that offer more range of motion tend to have more muscle fibers in...
series
Which two physics-based criteria are necessary for motion to occur?
space and time
Which kinematic metric involves a "rate of motion" with NO concern for direction?
speed
A trampoline is useful because it stores what type of energy?
strain energy
A bent pole vaulting pole is a good example of stored .
strain potential energy
Muscle Mechanics: Which of the following is NOT one of the primary components that dictate how much force a muscle can produce
temperature of the muscle
Electromyography - Which of the following represent the two motor control strategies that the CNS uses to increase muscle force?
temporal summation and spatial summation
Of the primary balance recovery strategies, which involves the simplest motor control response?
the ankle strategy
Even a short drop onto a hard surface (e.g. falling on ice) can be very painful because..
the short duration of impact (i.e. small time) results in a high impact force
An olympian throwing a discus spins around half a turn and throws a disc 55 meters. They then use a technique where they rotate 1.5 times (one full extra rotation) and throw a discus 60 meters. But, we know that rotating 10 times before throwing will not result in a throw that is farther than 60 meters. Why?
the thrower can only spin so quickly, and can only apply so much force at high speed, so they will likely reach the peak force and velocity well before 10 rotations
Which of the following is NOT true of concurrent forces?
they occur along the same line of action
A gymnastics landing mat increases what physics property so that the landing force is reduced?
time
This cardinal plane cuts the body into top and bottom halves.
transverse plane
"Displacement" is best modeled as a vector because it includes both distance AND direction.
true
Although changes could be made to improve the safety of many sports, many will never happen because they may impact performance in the sport (e.g. giving ice skaters skates with more padding in them).
true
An object does NOT need to be capable of "active" shortening to generate an internal force.
true
Biomechanics is a field of study that falls under the umbrella of "kinesiology".
true
Colinear forces always have the same line of action
true
Kinematics" refers to the study of motion.
true
Muscle Mechanics: Muscle force output is limited when a muscle is fully lengthened because fewer cross-bridges can be formed.
true
Muscle force output is limited when a muscle is fully lengthened because fewer cross-bridges can be formed
true
Our bodies are always exposed to, or experiencing, forces.
true
Positive work is being done to an object if the object displaces in the same direction as the force
true
The distribution and amount of different muscle fiber types within the muscle can impact the overall ability of a muscle to generate force.
true
The length/magnitude of a resultant vector from both vertical and horizontal component vectors can be found using the Pythagorean Theorem if we know the lengths of the component vectors.
true
When defined as a vector, a force has both magnitude and direction.
true
When we apply an impulse to an object, we can increase its momentum by increasing either the amout of force we apply, or the amount of time over which that force is applied.
true
er: High power exercises can increase the risk of injury, but may be worth incorporating into a training program to increase the specificity of training.
true
The displacement of an object divided by the time it took to complete that displacement is...
velocity
When we try to increase the momentum of an object during a throwing task (e.g. shotput or baseball pitching), what physics-based property are we trying to increase?
velocity
Which kinematic metric describes "rate of motion" in a specific direction?
velocity
Which of the following components of a projectile is affected by gravity?
vertical component
Which of the following does NOT represent one of the four systems discussed in class that is utilized by the body to evaluate one's balance
vestigial system
Which of the following is the correct unit for mechanical power?
watts
Which of the following mechanical quantities is not directly dependent on time or velocity (i.e. time and velocity are not part of the equation)?
work
To suggest that a body or object is "bilaterally symmetrical" means that
you can cut the object in such a way that one half is the same as the other (e.g. right and left sides of the body)
If linear velocity is constant, then acceleration is what?
zero
Linear Kinematics Basics: A runner completes one full lap around a 400 meter track and ends where they started. What is their displacement?
zero
A medicine ball with a mass of 9.1kg is thrown with a velocity of 8.9m/s over a distance of 2.4m. Assuming the total time of flight is 0.56 seconds, how much kinetic energy does the ball have while it's in the air?
360.4 joules
During the "World's Strongest Professor" competition, I was applying a 75N force to my 55kg moped to get it moving prior to jumping on to it. Calculate how fast (velocity) my moped will be moving after I apply this force for 8 seconds.
10.9 m/s
A 64kg person applies an average force of 50N to push a 90kg desk five (5) meters from one end of a classroom to another. If the entire process takes 20 seconds to complete, how much power did the person generate?
12.5 watts
A 75kg person does 40Nm of work to a 9kg dumbbell over a period of 2.5 seconds. Assuming the displacement is less than 10 meters, how much power did the person generate?
16 watts
A runner moving at a velocity of 6 meters/second increases velocity over a 2 second time interval to a rate of 10 m/s. What is the rate of acceleration? (Note: "^2" in the answer options means "squared")
2 meters/second^2
How much external torque is a 75N weight, by itself, placing on the elbow joint if the elbow is flexed to 90° and the forearm is 0.32 meters long?
24 nM
Which of the following gait metrics relies on temporal information?
Cadence
Which physics equation can be re-written to come up with the impulse-momentum relationship equation?
F=ma
Which of the following is NOT a type of locomotion?
Falling
All of the muscle fibers of a given motor unit tend to be "clustered" in a specific part of a given muscle.
False
Although momentum includes velocity which can be positive or negative, momentum is always positive.
False
Anatomical position involves the palms facing the side of the body.
False
Balance & Stability: The base of support (BOS) for a football lineman in a three-point stance is defined by an imaginary line surrounding only his feet.
False
Getting up out of a chair (from sitting posture to standing posture) typically involves eccentric contractions of your lower extremity muscles.
False
Golgi tendon organs are used by the balance system to determine muscle length and assess balance.
False
In order to increase torque, you can either increase the force that is applied, or increase how quickly you apply that force.
False
Isaac Newtons laws of motion help to explain movement of all materials in all realms of physics.
False
Measuring someone's static balance will give a clinician a very good idea of how they will perform during a dynamic stability test.
False
Muscle Mechanics: Muscles tend to generate the most force when they are shortened because there is maximum actin-myosin overlap.
False
Surface electrodes are more invasive and painful than indwelling electrodes because they require preparation of the skin, which can include shaving, abrasion and the application of alcohol swabs or other cleaning agents.
False
Telemetry-based EMG is advantageous because everything is connected by wires which reduces the likelihood of noise contaminating the signal.
False
The biggest difference between walking and running gait is that running has no stance phase.
False
A person is involved in a car crash and has a momentum of 2,050 kg*m/s. If the airbag deploys, the impact will occur over 0.1 seconds. If the airbag does NOT deploy, the impact will occur over 0.01 seconds. How will the impact force change if the airbag does NOT deploy?
Force will be 10 times greater compared to a situation where the airbag deploys
The area under an EMG activation curve is analogous to which kinetic quality?
Impulse
Impulse is calculated by which of the following equations?
Impulse = Force * time
The All-or-None Principle says which of the following?
When one muscle fiber within a motor unit fires, they all fire.
Which temporal/spatial gait metric specifically gets larger the more unstable someone becomes?
Step width
Although changes could be made to improve the safety of many sports, many will never happen because they may impact performance in the sport (e.g. giving ice skaters skates with more padding in them).
True
Because impulse includes Force which can be positive or negative, impulse can be positive or negative.
True
Biomechanics can help to improve sports equipment.
True
Biomechanics can involve the study of biological tissue.
True
For someone who displays healthy, symmetrical gait, step length should be approximately half of stride length.
True
Forces: Assuming the same amount of acceleration, it takes more force to accelerate an object with more mass than an object with less mass.
True
Humans are bilaterally symmetrical with respect to the mid-sagittal plane.
True
Impulse can be used to increase or decrease the momentum of an object
True
In anatomical position, the arms should be adducted to the side of the body.
True
Indwelling EMG represents the best technique for studying individual motor units within a muscle.
True
Muscles doing positive work would imply that the muscles were contracting concentrically.
True
One advantage of using indwelling electrodes, rather than surface electrodes, is that they allow the clinician/experimenter to assess the electrical activity of certain deep muscles.
True
Since acceleration involves change in velocity over time, it is directional and always has a sign (+/-).
True
The stance phase of the gait cycle represents the first 60% of the gait cycle.
True
The term "kinetics" refers to a field of study that is concerned with the FORCES that cause motion.
True
When we apply an impulse to an object, we can increase its momentum by increasing either the amout of force we apply, or the amount of time over which that force is applied.
True
What is generated when a muscle recieves a single stimulus?
a twitch
Which of the following best explains why a walker makes it safer for someone to walk? (reminder: a walker is the clinical device with four feet that sometimes also has wheels on the back legs, or all four legs)
a walker helps to increase someone's base of support which adds stability
From anatomical position, this movement occurs mostly in the frontal plane.
abduction & adduction
The phenomenon where muscle force is reduced because it is fully shortened is known as...
active insufficiency
What type of EXTERNAL torque is the shoulder experiencing when the shoulder is abducted to 90° (i.e. what is the external torque trying to make the arm do)?
adduction
Mechanical Work: Doing work to an object can have an effect on which of the following?
all of the above
Which of the following is/are correct formula(s) for mechanical power?
all of the formulas are correct
Which of the following is a way that you could increase your power?
all of the options would increase Power
How is it possible that a pilot can experience large G-forces during a turn in an airplane when the plane is maintaining a constant air speed?
because speed can remain constant while velocity in a given direction changes, resulting in large accelerations and forces
Which of the following is one reason that it is more difficult to walk on stilts?
because the small feet of the stilts mean that base of support is reduced
How can we BEST disrupt someone's vision to factor out visual cues for balance correction?
blindfold them
A force is applied to an object to make it slide. As the object slides, it does NOT spin so there is no rotation. This means that the force applied was perfectly...
centric
What type of muscle contraction is required of the quadriceps during the kicking and follow-through phases of kicking a ball (i.e. swinging the lower extremity anteriorly)?
concentric
What type of muscular contraction is associated with positive mechanical work?
concentric
When shooting a foul shot in basketball (i.e. pushing the ball toward the hoop) the triceps are performing what type of muscle contraction?
concentric
Imagine someone pushing a door open. The closer someone places their hand to the hinges of the door, the more their torque will... (assume that force is always the same)
decrease
A situation where someone is pedaling a bike while rolling down a curved hill is best described as which type of motion (if you want, you can also assume that they are flapping their arms like wings)?
general motion
A javelin thrower has a maximum throwing force of 800N. To increase the release velocity of the javelin, the thrower uses a technique that allows the throw to occur over a longer period of time. Based upon the compensation described above, what kinetic feature was the thrower manipulating to get a higher release velocity?
impulse
Impulse is calculated by which of the following equations?
impulse = Force * time
What can be done to increase the tension (i.e. force) in a single motor unit?
increases stimulus frequency
Which of the following is the best example of manupulating impulse to increase momentum when force is maxed out (i.e. no more force can be applied but we want to increase impulse, which will increase momentum).
increasing the amount of wind-up (i.e. time) for a pitch
A car's speedometer depicts..
instantaneous speed
From anatomical position, this movement occurs mostly in the transverse plane.
internal & external rotation
What type of muscular contraction is associated with NO mechanical work?
isometric
What happens to the EXTERNAL torque that our elbow experiences as we move from anatomical position to 90° of elbow flexion
it increases
A hockey goalie's glove is able to reduce the momentum of a hockey puck because...
it increases the time of impact
Often, a tight rope walker will hold a long pole down below their waist. What impact does this have on their center of mass, which would improve stability?
it lowers their center of mass
Anatomical position is important because it allows us to define
kinematics
A skydiver in free fall has what type of energy?
kinetic energy
