Biomechanics Final
The elbow is located at (15,31).The wrist is located at (30,50).Where is the center of mass of the forearm for someone with a segment length percent of 45.74%?
(21.9, 39.7)
if a biker was peddling at 15 m/s into a 5 m/s headwind, the relative velocity would equal to?
-20 m/s (-15m/s + (-5m/s) = -20 m/s).
Alice generates an angular velocity of 3600 deg/s with a radius of rotation of 0.5 m immediately before impact in a tennis serve. What is the linear velocity of the racquet?
v=wr - convert to radians Velocity (m/s): 31.4
drafting difference of importance in running vs cycling?
when running behind someone, the air pressure and relative velocity are both decreased, allowing the runner to use less energy to overcome drag force. in cycling the relative velocities of air are higher, so riders use more energy to overcome air resistance. Rare in cycling to see an early breakaway reach the finish line first. in running it is quit common to see an early break away to reach the finish line first. in running about 6-12% of energy is used to overcome air resistance so in cycling drag forces are much more meaningful. faster the riders speed, the more effective drafting becomes. (velocity is squared in drag force equation!!!) drag force increases EXPONENTIALLY with riding speed.
frontal plane :
The plane that splits the body into anterior and posterior halves.
sagittal plane :
The plane that splits the body into right and left halves.
turbulent flow
when the object's velocity is to high or the curvature of the object's surface is too large the deflected molecules do not make it back to the surface and bounce about chaotically, not in the smooth parallel layers.
Suppose this same biker got tired and slowed down to 5 m/s with the same 5 m/s tail wind. What would the relative velocity be equal to now?
The relative velocity would be - 5 m/s + 5 m/s = 0 m/s.
Muscle Activation
When a motor unit is stimulated, acetylcholine (ACh) is released to the sarcolemma (muscle membrane). The interaction of ACh with gates on the sarcolemma allows positively charged sodium (Na+) to flow into the negatively charged intracellular space. Initially, the electrical potential is -90 mV between the intra and extracellular space. The entry of Na+creates a signal that travels to the myofibrils within the muscle fiber. When the Na+ ions arrive, they precipitate the release of Calcium ions (Ca2+) which are used with ATP to contract the muscle at the actin/myosin level. Once the voltage shifts from -90 mV to around -55 mV, the series of events that lead to muscle activation occurs. This will occur anywhere from 10-500 Hz.
how can athletes influence surface drag?
athletes cant really control the fluid viscosity but they can alter the surface texture by wearing smooth, skin tight clothes. rougher surfaces create more friction between the object surface and the fluid molecules it is travelling through.
how could curved baseball throws be explained?
bernoullis principle and magnus effect
Air density is based upon A: Air pressure B: Temperature C: Humidity D: All of the above
d all
what determines fluid density? List from most to least important.
fluid pressure, temperature and humidity.
describe the 3 fiber arrangements & give ex
fusiform- muscle belly is wider than origin or insertion, ex biceps brachii. unipennate- fibers are arranged to insert diagonal to the tendon, ex extensor digitorum longus bipennate- two rows of muscle fibers facing opposite directions run diagonally towards a central tendon, ex rectus femoris
Calculate the magnitude of the angular momentum if an object's moment of inertia is 50 kg·m·m and its linear velocity is 10 m/s. 5 50 100 500 need more information to calculate
need more information to calculate
extrinsic factors
related more directly to the activity vs the participant. Nature of task (how fast/intense/ long), opponent level, equipment, playing surface, weather
sarcolemma, endomysium, perimysium, epimysium, and muscle tendon
sarcolemma- cell membrane that surrounds every striated muscle fiber, no contractile properties. endomysium- surrounds the sarcolemma and contains capillaries, nerves, and lymphatics. perimysium- a sheath of connective tissue surrounding fasicles, or groups of muscle fibers epimysium- layer of connective tissue that surrounds an entire muscle muscle tendon- connects muscle to bone
drag force
the dynamic fluid force working in opposition to the direction of motion of an object. resists the motion of a body through the fluid and tends to slow velocity.
describe elbow flexion & extension in terms of axes and planes.
the elbow performing flexion and extension is always considered rotating around the transverse axis and is parallel to the sagittal plane.
terminal velocity
the maximum velocity that a falling object can achieve under the influence of gravity. when the air resistance (force of drag) equals force of gravity.
If the elbow is located at (1.37, 1.20) and the wrist is located at (1.71, 1.35), where is the center of mass of the forearm located? (The length percent for the forearm is 43%.) (1.22, 1.14) (1.52, 1.14) (1.22, 1.26) (1.52, 1.26)
(1.52, 1.26)
radius of gyration
(K) The radius of gyration is the root mean square distance of each point on an object relative to its center of mass. The root mean square is caluculated by squaring the distance from the center of mass to every point on the object, adding those distances together, then taking the square root of that sum.
If the biker was peddling at the same speed but with a 5 m/s tail wind, the relative velocity would then equal to?
-10 m/s (-15m/s + (5m/s) = -10 m/s).
calculate force production using cross sectional area
. Physiological cross-sectional area is usually calculated by multiplying the cross-sectional area mentioned previously by the cosine of the pennation angle. Force production capability of a skeletal muscle is often estimated by multiplying the physiological cross-sectional area by the magnitude of force that can be produced by a certain cross-sectional area of muscle.
There are numerous factors that influence your ability to produce active muscle force using your skeletal muscles. The factors that will be discussed within this chapter are: (6- define each)
1.muscle cross-sectional area- area perpendicular to its length 2. fiber arrangement-The organization of the fibers that make up muscle tissue (parallel, unipennate, multipennate) 3. fiber length- The long measurement of muscle fibers. Fiber length is connected to the range of motion of muscle and contraction velocity. 4. contraction velocity- The velocity of muscle shortening or lengthening. 5. fiber type-A category of muscle matched with its ability to produce force and resist fatigue. Specifically, the type of myosin and degree of oxidative phosphorylation determines fiber type. 6. neuromuscular factors
During a drive by golfer Tiger Woods, the angular velocity of his club is zero at the top of the backswing and 30 rad/s at the bottom of the downswing just before impact with the ball. If the downswing lasts 0.30 s, what is the average angular acceleration of the club during the downswing? 10 rad/s 30 rad/s/s 1.0 rev/s/s 100 °/s/s 100 rad/s/s
100 rad/s/s
A baseball bat swings with a linear velocity of 30 m/s. If the radius of rotation is 1.18 m, what is the angular velocity in deg/s? 1457 deg/s 25.4 deg/s 742 deg/s 325 deg/s
1457 deg/sec
Most common lever system in the body and why
3rd class since the effort arm (distance from the joint axis to the line of force of the muscle) is relatively short. Third class levers will always have a shorter effort arm than resistance arm. This will create a mechanical advantage geared more towards speed and range of motion than strength.
For any given muscle, the moment arm is largest when the angle of pull on the bone is closest to 0° 45° 90° 180° It depends upon the segment
90
A discus thrower exerts a torque of 1.9 Nm on a 2 kg discus. The discus has a radius of gyration of 10 cm. If this is the only torque exerted on the discus, what is its angular acceleration? 95 rad/s/s 9.8 m/s/s 95 rev/s/s 95 °/s/s 9.5 rad/s/s
95 rad/s/s
how can a change in angular momentum affect an object?
A change in angular momentum can affect an object in four ways. First, as we have discussed, it can result in a change in the object's angular velocity. Second, it may result in a change in the direction of the axis of rotation. Third, it may result in a change in the object's moment of inertia. Fourth, some combination of the first three possibilities may occur
The force-velocity relationship of muscle.
A combination of muscle action type (concentric, eccentric, or isometric) and action velocity is also known to influence force production capability. force production capability decreases as the velocity of concentric muscle actions increases. One potential explanation for this observed phenomenon is that as concentric velocity increases, the actin and myosin filaments slide by one another so quickly that some of the binding sites are missed and force production decreases. Second, force production capability increases as the velocity of eccentric muscle actions increases. This increased force production during eccentric muscle actions may be related to passive force that results from stretched, inactivated sarcomeres
1st Class Lever System:
A first class lever has the fulcrum (axis of rotation) in between the effort and resistance forces. Like a seesaw with fulcrum in the middle. Example is neck. neck is fulcrum, weight of your head/face is load on one side of the fulcrum, resistance is the muscles in the back of your neck applying force to lift your head up.
anterior-posterior axis :
A horizontal axis in the anterior/posterior direction. line going in your back and coming out of your belly button.
transverse axis :
A horizontal axis through the medial/lateral direction. line going in one hip and coming out of the other
2nd Class Lever System:
A second class lever has the resistance force in between the fulcrum and effort force. Load is in the middle. example is ankle. pivot point is toes, load is body weight, force is generated up by the calf. think wheelbarrow.
3rd Class Lever System:
A third class lever has the effort force in between the fulcrum and resistance force. Load is on outside, resistance is in middle. example is bicep and most hinge joints (think curl). elbow is fulcrum, tendon connects to forearm and load is held in hands. think tweezers or shovel
Wolff's Law:
A tissue adapts to the level of stress imposed upon it; The level of adaptation reflects the level of typical loading. As stresses are placed upon the body, any tissue that received blood flow will gradually adapt to those stresses. This can lead to an increased ability to withstand stresses (when stresses are greater than the tissue is accustomed to) or a decreased ability to withstand stress (when stresses are lower than the tissue is accustomed to). unless! the tissue is pushed to the point of injury Tissues are also very specific in how they are trained. If someone trains with a low stress and high frequency, there will be greater improvements in those conditions, but not so much in high stress low frequency situations.
longitudinal axis :
A vertical axis in the superior/inferior direction. Head to feet.
Which activity would most likely have the center of mass outside the body? A: Piked position in diving B: Running C: Swimming D: Basketball jump shot
A: Piked position in diving
What is the main plane and axis of motion at the hip for punting a football? A: Sagittal plane/Tranverse axis B: Frontal plane/Anterior-Posterior axis C: Transverse plane/Longitudinal axis
A: Sagittal plane/Tranverse axis
EMG provides a voltage reading telling the... A: Voltage difference between two locations over a muscle B: The voltage at one location on muscle C: The current flowing along muscle
A: Voltage difference between two locations over a muscle
A mechanical advantage below one... A: shifts away from strength towards speed B: shifts away from speed towards strength C: gives an optimal combination of speed and strength for all activities D: is only found in the human body Next Prev
A: shifts away from strength towards speed
diving & CONSERVATION OF ANGULAR momentum
Although total body angular momentum when the sum of external torques is zero, an athlete can transfer angular velocity from one part of the body to another, which changes the amount of angular momentum associated with different parts of the body. diving shows how the velocities of the transverse and longitudinal axes change while total angular momentum of the body stays constant. After the diver leaves the springboard, his upper body has a greater angular velocity than his lower body. As he completes the somersault, he kicks his legs out, transferring angular momentum to his legs. This changes the moment of inertia of his whole body and slows the rotation of the somersault. Now he has to switch axes of rotation and start rotation about the long axis of his body. He does this by changing the orientation of his body and initiating a twisting rotation. Throughout this whole process, he maintains the angular momentum that he left the board with. How he uses his body and manipulates the angular momentum throughout the dive dictates whether or not the dive is successful.
moment of inertia - symbol and definition
An object's resistance to a change in angular motion. I=mk (radius of gyration) squared, when an object is rotating about its center of mass.
A 2.0 -kg object is spinning around its center of mass. The radius of gyration is 15 cm. What is the object's angular inertia around its center of mass?
Angular Inertia (kgm2):0.045
A 0.8 -kg baseball bat is swinging at 155 rad/s. The radius of rotation is 1.21 m. The bat has a radius of gyration of 0.22 m. What is the angular inertia of the bat?
Angular Inertia (kgm2):1.21
example of altering bodys moment of inertia in sports
As seen in figure skating and diving, athletes take advantage of altering the moment of inertia of their whole bodies to perform various tasks, regardless of which axis they are rotating around. When a diver or gymnast needs to complete a certain number of flips in the air, they will rotate in a tucked position, rather than laid out (or stretched out). This position decreases the moment of inertia of the body as they complete the required rotations.
What is the main plane and axis of motion for a cartwheel? A: Sagittal plane/Tranverse axis B: Frontal plane/Anterior-Posterior axis C: Transverse plane/Longitudinal axis
B: Frontal plane/Anterior-Posterior axis
A 0.4 kg baseball bat has a radius of gyration about a transverse axis through its center of gravity of 0.36 m. When a player swings, the axis of rotation is 0.75 m from the center of gravity of the baseball bat. What is the moment of inertia relative to the swing axis? Between 0 and 0.25 kgm2 Between 0.25 and 0.50 kgm[2 Between 0.50 and 0.75 kgm2 Between 0.75 and 1.00 kgm2
Between 0.25 and 0.50 kgm[2
What is the initial drag force for a golf ball with the following conditions? Frontal area: 14 cm2 (remember to convert to m2), air density: 1.204 kg/m3, initial velocity: 50 m/s2, coefficient of drag: 0.3 Less than 0.25 N Between 0.25 and 0.50 N Between 0.50 and 0.75 N More than 0.75 N
Between 0.50 and 0.75 N
A 90-kg (including any equipment) skydiver drops out of a plane and aims his body head first towards the ground. Using an air density of 1.0 kg/m3, a frontal surface area of 0.3 m2, and a drag coefficient of 0.4, what will the skydiver's terminal velocity be? Less than 50 m/s Between 50 and 100 m/s Between 100 and 150 m/s More than 150 m/s
Between 100 and 150 m/s
If the hip is located at (2.30, 4.95) and the knee is located at (2.54, 5.55), what is the horizontal part of the center of mass coordinate? (The length percent for the thigh is 43%.) Less than 1.5 Between 1.5 and 2.0 Between 2.0 and 2.5 More than 2.5
Between 2.0 and 2.5
What would the weight on the scale show for the following situation? The person's center of mass is 0.9m of his height. His mass is 75 kg. The board weighs 30 N and has a length of 2 m. Less than 300 N Between 300 N and 350 N Between 350 N and 400 N More than 400 N
Between 300 N and 350 N
If the hip is located at (2.30, 4.95) and the knee is located at (2.54, 5.55), what is the vertical part of the center of mass coordinate? (The length percent for the thigh is 43%.) Less than 5.0 Between 5.0 and 5.25 between 5.25 and 5.50 More than 5.50
Between 5.0 and 5.25
Immediately before the impact of a golf club with a golf ball, the club is rotating at 1375 deg/s with a radius to the clubhead of 1.6 m. What is the centripetal acceleration of the clubhead? Less than 50 m/s/s Between 50 and 500 m/s/s Between 500 and 1000 m/s/s Between 1000 and 1500 m/s/s More than 1500 m/s/s
Between 500 and 1000 m/s/s
Consider the following situation. A 689 N person lies down on a 2 m, 30 N board. Their feet are exactly at the fulcrum. They are 1.75 m tall. The scale reads 330 N. Where is their center of mass as a percent of their height? Less than 50% Between 50 and 52% Between 52 and 54% The force created by the fulcrum is equal to the force created by the scale. More than 56%
Between 52 and 54% person N(distance to com) +SB (.5 SB Length) = scale reading (SB length)
What is the drag force exerted on a runner running at 7 min/mi pace (3.83 m/s) on a day with no wind? Assume a coefficient of drag of 0.8, an air density of 1.204 kg/m3, and a frontal surface area of 1.0 m2. Less than 7 N Between 7 and 8 N Between 8 and 9 N Between 9 and 10 N More than 10 N
Between 7 and 8 N
Calculate the moment of inertia of a skater with a mass of 52 kg with a radius of gyration of 0.15 m that is spinning around her longitudinal axis. Less than 1.0 kgm2 Between than 1.0 and 2.0 kgm2 Between than 2.0 and 3.0 kgm2 Between than 3.0 and 4.0 kgm2 More than 4.0 kgm2
Between than 1.0 and 2.0 kgm2
Parallel myofibrils compared with series myofibrils have... A: Greater range of motion and greater force production B: Lower range of motion and lower force production C: Lower range of motion and greater force production D: Greater range of motion and lower force production
C: Lower range of motion and greater force production
The perpendicular distance in the torque equation represents: A: The force B: The line of force C: The moment arm D: The parallel distance to the axis of rotation
C: The moment arm
What is the main plane and axis of motion for a spin in skating? A: Sagittal plane/Tranverse axis B: Frontal plane/Anterior-Posterior axis C: Transverse plane/Longitudinal axis
C: Transverse plane/Longitudinal axis
If we define stability as 'the ability to return to equilibrium after being displaced', then stability can be increased by... A: decreasing the size of the base of support B: increasing height C: decreasing weight D: increasing weight
C: decreasing weight
The center of mass of someone's thigh, shank, and foot are located at the following coordinates: Thigh: (2.7, 3.2) Shank: (2.1, 2.5) Foot: (1.5, 1.9) If the masses of them are respectively 9.6, 2.9, and 0.9 kg, where is the location of the entire leg?
CM= (2.5, 3)
Pronation of the foot and ankle includes: A: Ankle eversion, plantar flexion, and sub-talar joint adduction B: Ankle inversion, dorsi-flexion, and sub-talar joint adduction C: Ankle inversion, plantar flexion, and sub-talar joint abduction D: Ankle eversion, dorsiflexion, and sub-talar joint abduction
D: Ankle eversion, dorsiflexion, and sub-talar joint abduction
What is true about the force-velocity relationship of muscle? A: Force increases as velocity increases concentrically and eccentrically B: Force increases as concentric velocity increases C: Force decreases as eccentric velocity increases D: Force decreases as concentric velocity increases
D: Force decreases as concentric velocity increases
The elbow is always this type of lever. A: First class B: Second class C: Third class D: It depends upon which muscle group is being used and where the resistance is coming from
D: It depends upon which muscle group is being used and where the resistance is coming from
The number of radians is calculated by: A: The angle divided by radius B: The radius divided by the angle C: The radius divided by the arc length D: The arc length divided by the radius
D: The arc length divided by the radius
Muscle has the greatest force ability when... A: When the muscle is at its greatest stretch B: When the muscle is at its shortest length C: Force production is equal at all lengths D: When the greatest number of actin and myosin are overlapping
D: When the greatest number of actin and myosin are overlapping
A power spectrum of EMG provides the frequencies present in the signal. These frequencies provide information for... A: Understanding peripheral fatigue B: Determining active fiber types C: Magnitudes of activation D: Only A & B E: A, B, & C
D: a and b
Limbs that are tapered (proximal ends are more massive than distal) allows for: A: Rotation of limbs with greater accelerations B: Rotation of limbs with a lower metabolic cost C: Linear accelerations of limbs require a lower metabolic cost D: Both A and B
D: a&b
If we define stability as 'the ability to maintain equilibrium', then stability can be increased by... A: decreasing the size of the base of support B: increasing height C: decreasing weight D: increasing weight
D: increasing weight
An airplane is taking off with the following conditions: Drag coef: 0.14 Lift coef: 1.2 Frontal area (m2): 87 Total surfacearea (m2): 920 Air density (kg/m3): 1.13 Ground vel (m/s): 135 Headwind (m/s): 12 Drag (kN), Lift (kN)??
Drag (kN):149 Lift (kN): 13479
Stress Strain curves
Elastic, yield point, plastic, ultimate strength/ failure In the elastic region, when the load creating the stress and strain is released, the tissue will return to its original shape and length. If the tissue enters the plastic region, some of the deformation will remain when the load is released. If the load creates too much stress or strain, it will reach the ultimate strength (also known as failure). This is where complete rupture or fracture will occur.
v=wr when to use
Even when an object is rotating, any point on the object can be described with a linear velocity. The further away from the axis of rotation, the greater the linear velocity will be This is useful to think about with golf clubs. As long as the same angular velocity can be generated, the longer the club, the greater the clubhead speed can be
drag force equation what to remember about each part?? (3)
F(d)= .5(coefficent of drag Cd) (p, density of the fluid) (frontal surface area) (velocity squared) frontal area can also be called the cross sectional area perpendicular to the direction of flow V is RELATIVE velocity of the object with respect to the fluid. A is in meters squared
Why is it recommended that you flex your knees and hips when lifting a heavy object rather than just flexing your hips and back? Flexing at the knees and hips decreases the resistance arm and torque at the lumbar spine. Flexing at the knees and hips increases the resistance arm and torque at the lumbar spine. Flexing at the knees and hips increases the overall vertical force. Flexing at the knees and hips decreases the overall vertical force.
Flexing at the knees and hips decreases the resistance arm and torque at the lumbar spine.
Alice builds up to an angular velocity of 972 deg/s with a radius of rotation of 1.34 m. If the hammer has a mass of 4.0 kg, what centripetal force will be required for her to keep balanced?
Force (N): 1542 find centripetal force then f=ma
factors affecting stress to tissues (5)
Force magnitude Area of force distribution Direction of force Loading rate Frequency
formula for force of gravity pulling down a slope
Fs = -mg sin(θ) find out what cos was from midterm flashcards
tissues and the kind of stresses they can best tolerate
Generally speaking, our bones can bear greater compressive stress than shear and tensiles stresses. CompacT boneS.. CTS, compression tensile then sheer The arrangement of collagen within tendons allows tendons to bear greater tensile stress than compressive and shear stress. Tendons Tensile best Also due to a unique arrangement of collagen, ligaments are able to bear greater shear stress, relative to tendons, and are also able to effectively bear tensile stress.
How much force do the knee extensors need to exert to produce an angular acceleration of 15 rad/s2? The mass of the lower leg and foot are 7.34 kg, the radius of gyration is 23 cm, and the knee extensors insert on the tibia at an angle of 70° at a distance of 6 cm from the axis of rotation at the knee.
I=mk^2 then T = Iα then T=Fd F=127 N draw diagram of knee and use SOHCAHTOA
figure skaters & conservation of angular momentum
In order do in air spins the skater needs to generate a lot of angular momentum. When a skater is in the air, no external torques are being applied to the body. Therefore, the skater needs to generate all the necessary angular momentum before leaving the ice. The ability to complete the rotations is dependent on how fast they can spin in the air (angular velocity). Once the skater has left the ice, there is an inverse relationship between moment of inertia and angular velocity (H=Iw). Since they are probably not losing mass in the air, the change in moment of inertia throughout the flight phase of the jump will only be related to changing body position (or the distribution of the mass). When the skater takes off for a jump, his arms are extended away from the body. Once in the air, he pulls his arms in close to his trunk, decreasing his moment of inertia and, since H is constant, increasing his angular velocity. In order to stop rotating before he lands, he repeats the process in reverse - he extends his arms (increasing his total body moment of inertia) and slows rotation.
Conservation of Angular Momentum
In the absence of external torques, the total angular momentum of a given system remains constant. However, even under these conditions, moment of inertia and angular velocity can change.
What happens to the centripetal acceleration when angular velocity doubles? It stays the same It also doubles It quadruples
It quadruples
When a moment arm is cut in half, what will happen to the amount of torque if the force is maintained? It will stay the same. It will double. It will be cut in half. None of the above
It will be cut in half.
While in the air a jumper raises his legs, what will happen to the rest of his body (relative to ground level)? It will drop lower. It will also raise. It will stay the same. It will spin around.
It will drop lower.
As angular velocity is increased, what will happen to the amount of centripetal force required if the radius is maintained? It will increase by the square of how many times the angular velocity increased (if the angular velocity doubled, then the centripetal acceleration would quadruple). It will increase linearly with angular velocity increases. It will not change. It will decrease.
It will increase by the square of how many times the angular velocity increased (if the angular velocity doubled, then the centripetal acceleration would quadruple).
T = Iα
Just as a linear force applied to a mass produces a linear acceleration (F = ma), a net external torque applied to a mass produces an angular acceleration (T = Iα)
Immediately before the impact of a golf club with a golf ball, the club is rotating at 1375 deg/s with a radius to the clubhead of 1.6 m. What is the linear velocity of the clubhead? Less than 50 m/s Between 50 and 500 m/s Between 500 and 1000 m/s Between 1000 and 1500 m/s More than 1500 m/s
Less than 50 m/s
connection Between Linear and Angular Kinetics Linear Angular m mass ? F Force ? L Linear Momentum ?
Linear Angular m mass I Angular inertia F Force T Torque L Linear Momentum H Angular Momentum
Connection Between Linear and Angular Kinematics Linear x position v velocity a acceleration
Linear Angular x position θ angle v velocity ω angular velocity a acceleration α angular acceleration
The perpendicular distance from the joint center of the ankle to the line of force through the Achilles tendon is 4.1 cm. The ground is pushing on the forefoot at a perpendicular distance to the ankle joint of 15.5cm. What is the mechanical advantage of this lever system?
MA= .26
emg
Muscle activation leads to a change in electrical potential around muscle membranes. Using surface electrodes or fine wires placed inside muscle, the electrical potential can be measured similar to how a voltmeter measures the electrical potential on a battery The voltages measured using electromyography (EMG) can be measured many times per second providing the frequency and amplitude of electrical potential changes which provide much useful information about the activation of muscle.
Active muscle force
Muscle tension stimulated from the neural system to imitate muscle contraction. a result of actin and myosin crossbridges.
The SI units for torque are : ft lb N Nm J none of the above
Nm
eccentric axis
Objects can rotate around many different axes. However, in many cases, we often force objects to rotate around an axis that does not go through its center of mass. Examples include swinging a tennis racquet, a baseball bat, or a golf club. An axis that does not go through an object's center of gravity is called an eccentric axis. This makes calculating the moment of inertia slightly more complex. use formula I= mk^2+ mr^2
angular momentum & golf clubs
Often, one of the goals of hitting a golf ball is to transfer a large amount of linear velocity to the ball. If the golfer can develop a large amount of angular momentum with the club, there is a greater potential to transfer more linear velocity to the ball. How can the golfer develop a lot of angular momentum? Remember the factors that influence angular momentum - mass of the object, distribution of the mass, and the angular velocity of the object. So a heavier, longer golf club swung at the same angular velocity as a shorter, lighter one will have more angular momentum. This comparison of angular momentum is only valid if both clubs are swung at the same angular velocity. Of course this is more difficult with an object of greater mass, or an object that's longer (once again, due to the moment of inertia of the object).
fluid forces present in swimming?
Only three fluid forces exist (buoyancy, drag, and lift)
what causes the resistance in angular motion?
Resistance is caused by the mass of the object and the distribution of that mass relative to the axis of rotation. this value of resistance is the moment of inertia (i). the amount of force that must be applied to move a static object when considering angular motion.
Transverse Axis- which plane corresponds?
Sagittal Plane- think flex/ext
joint actions in FRONTAL PLANE/ANTERIOR-POSTERIOR AXIS
Shoulder Abduction Shoulder Adduction Ulnar deviation Radial deviation Hip Abduction Hip Adduction Ankle inversion Ankle eversion Lateral flexion
joint actions in SAGITTAL PLANE/TRANSVERSE AXIS
Shoulder Flexion Shoulder Extension Elbow Flexion Elbow Extension Wrist Flexion Wrist Extension Hip Flexion Hip Extension Knee Flexion Knee Extension Plantar Flexion Dorsiflexion Trunk Flexion Trunk Extension Neck Flexion Neck Extension
how to determine if an object will float
Specific gravity is one way to determine if an object will float. Specific gravity is defined as the weight of an object divided by the weight of an equal volume of water. If the specific gravity is 1.0 or less, that object will float. Another way to determine the floatability of an object is density. Density is the ratio of mass to volume (Equation 1). The density of water is approximately 1000 kg/m3. If an object is less dense than water, that object will float. In the human body, muscles and bones have densities greater than 1000 kg/m3, however, fat has a density less than 1000 kg/m3. Someone with low body fat may find it harder to float than someone with a higher body fat content. Breathing, however, does contribute to the total body density, as the volume in the chest cavity increases during inhalation and decreases during exhalation.
angular impulse-momentum relationship is represented by formula:
T delta t = deltaI deltaw angular impulse=angular momentum
Tangential Acceleration
Tangential acceleration is the linear acceleration of a point on a rotating object in the direction it is traveling at some instant in time. It is equal to the angular acceleration (α) multiplied by the radius of rotation (r). The angular acceleration must be entered in radians per second squared.
There are three primary categories of stress applied within the human body: .NAME THEM AND DESCRIBE. Each category is based on direction of the stress, relative to the long axis of the biological structure (e.g., bone, muscle, tendon, or ligament)
Tensile stress acts parallel the long axis of a biological structure and tends to elongate the structure. Compressive stress also acts parallel to the long axis of a biological structure, however, compressive stress tends to shorten the structure. Shear stress acts in a direction that is perpendicular to the long axis of the biological structure
density
The density of water is approximately 1000 kg/m3. If an object is less dense than water, that object will float. In the human body, muscles and bones have densities greater than 1000 kg/m3, however, fat has a density less than 1000 kg/m3. Someone with low body fat may find it harder to float than someone with a higher body fat content.
Effort arm
The effort arm is the person or object generating force to work against some resistance force.
What would happen if someone on the spine board fully abducts at the shoulder (hands as far from the feet as possible)? The center of mass would drift towards the feet The force on the scale would increase The percent height of center of mass would decrease The fulcrum would receive a greater force
The force on the scale would increase
Where is the intersection of axes and planes?
The intersection point of these axes and planes is the center of mass of the body while in anatomical position. When someone goes out of anatomical position, the intersection point stays where it was (somewhere in the pelvis).
centripetal acceleration definition
The linear acceleration of an object directed towards the axis of rotation. This is the acceleration that leads to a rotation of the object.
center of mass & body possitioning
The path of the center of mass during flight is fixed by projectile motion equations. Body positioning can change which leads to center of mass changes relative to the body, but not relative to the ground.
strain :
The percent change in length of a tissue relative to it's original length. Strain usually results from stress. In other words, when a force is applied to a biological structure, stress results and that structure may change shape (deform).
centrifugal force - definition and which newtons law it relates to
The reaction to centripetal force. This force is directed away from the axis of rotation. Newton's third law of motion states that every action has an equal and opposite reaction. In this case the reaction to the centripetal force is called centrifugal force and is directed away from the axis of rotation.
moment off inertia in human body
The shape of the human body influences its moment of inertia. The majority of our mass is located closer to the center of mass. Our limbs are relatively light compared to our trunk. Additionally, our segments are tapered - decreasing in size and mass as you get further from the attachment to the trunk. Again, more mass located closer to the "middle" of the body decreases the moment of inertia of the body
what do you need to remember about ALL angular kinematics formulas?
The standard label for angular position for the SI unit system is the radian. All of the formulas in this chapter require calculations to be completed using radians. There are 2 π radians in a full circle (360°). Converting from radians to degrees will require multiplying by 360°/2π . Converting from degrees to radians will require multiplying by 2π/360°.
bouyant force, when will an object sink or float?
The upwards force on an object in a fluid equal to the weight of the volume of the fluid displaced. If the buoyant force exerted by the fluid is greater than or equal to the weight of the object, that object will float. If the buoyant force exerted by the fluid is less than the weight of the object, that object will sink.
When initial velocity is increased, what happens early in the flight of a golf ball? There is a greater upwards acceleration and less slowing down of the ball There is a greater downwards acceleration and less slowing down of the ball There is a greater upwards acceleration and more slowing down of the ball There is a greater downwards acceleration and more slowing down of the ball
There is a greater upwards acceleration and more slowing down of the ball aka more lift and drag
When the spin rate changes from 2000 to 3000 rpm during backspin, why is more lift produced? There is a greater velocity of flow under the ball, than on top There is a greater velocity of flow above the ball, than on below The Magnus Effect is decreased as spin rate increases
There is a greater velocity of flow under the ball, than on top
A leg is swinging through knee extension at 458 deg/s. To stop the knee extension in 0.2 s, how much torque must be generated by the knee flexors? Angular inertia of the lower leg and foot is 0.7 kgm2.
Torque (Nm): -28
A hammer thrower takes the angular velocity of the hammer from 450 deg/s to 920 deg/s in 4.5s. The angular inertia of the hammer is 20 kgm2. What is the average torque required to generate this acceleration?
Torque (Nm):36.5
Longitudinal Axis- which plane corresponds?
Transverse Plane- think shoulder IR, shoulder horizontal abd
During running, what is the main axis and plane corresponding with the joint motions? Longitudinal axis / Transverse plane Anterior-posterior axis / Frontal plane Transverse axis / Sagittal plane Transverse axis / Transverse plane
Transverse axis / Sagittal plane
A diver attempts a 1 1/2 front flip in a tuck position off the 1 m board, but only rotates 1 1/4 times (ouch!). Which of the following suggestions in not appropriate for the diver? Jump higher Tuck looser Tuck sooner Release tuck later Generate more angular momentum
Tuck looser
A 75-kg skier is gliding down a slope of 30 deg. The drag coefficient is 0.8 . The air density is 1.1 kg/m3. the frontal surface area is 0.9 m2. Ignoring friction between the skis and ground, what will be his terminal velocity?
Vel (m/s): 30.5
When is it possible to generate very large resistance forces?
When the effort arm is longer than the resistance arm. However, this compromises speed.
I= mk^2 + mr ^2 when to use vs. I=mk^2
When the object is not rotating around its center of mass, this equation should be used. The angular inertia (I) around the axis (b) equals mass (m) times the radius of gyration squared plus the mass (m) times the radius of rotation (r) squared. use I=mk^2 when an object is rotating about its center of mass
Mechanical Advantage
When the ratio of effort arm to resistance arm is not equal to 1, there will be either a strength or speed advantage. However, we can position our body relative to the resistance force to modify the mechanical advantage to shift more towards strength or speed. In human body MA is usually less than 1, meaning greater speed and ROM over stregnth. MA= EA/RA
When is torque generated in a lever system?
Whenever a lever system is in place, the resistance and effort forces will both generate torques around the fulcrum
Bernoulli's Principle tells... A: Faster moving fluids exert less pressure laterally than slower B: Slower moving fluids exert less pressure laterally than faster C: Faster moving fluids exert less pressure longitudinally than slower D: Slower moving fluids exert less pressure longitudinally than faster
a Faster moving fluids exert less pressure laterally than slower
two types of fluid forces exerted on an object:
a buoyant force which is a vertical force due to immersion in a fluid, and a dynamic force which is due to relative motion in a fluid.
Which muscle has the greatest range of motion with the smallest force production? A: Fusiform B: Unipennate C: Bipennate
a fusiform
The effect from molecules of a fluid being slowed more on one side than another of a spinning object is called: A: The Magnus Effect B: Bernoulli's Effect C: Archimedes Principle D: Ibigawa's Effect
a magnus
Torque
a rotary push or pull of an object created by having a force offset from an axis of rotation.Created when a force is applied some distance from the axis.
What is the main joint action at the shoulder during the up phase of a wide-grip pull-up? Adduction Abduction Horizontal Adduction Horizontal Abduction
adduction
for every torque exerted by a body (or body segment),...
an equal and opposite torque is exerted onto that body. newtons 3rd law
cross sectional area
area of the muscle that is perfendicular to the pull of the muscle force. muscle force is proportional to this area, relates to the ability to produce active muscle force.
What effect will using a longer golf club have on linear velocity of the clubhead if a matched angular velocity is used? A: It will not change B: It will increase C: It will decrease
b increase
What happens to force production in muscle as cross-sectional area increases? A: It increases exponentially B: It increases linearly C: It decreases D: Cross-sectional area does not affect force production
b increase linearly
If the density of an object is less than the density of a fluid... A: It will sink B: It will float C: It will stay in place and not sink or float
b it will float
Mike spins with an angular velocity of 7 rad/s when he begins the throwing motion of a discus. Just before the release, he is rotating 22 rad/s. If the throwing motion took 0.2 s, what was Mike's average angular acceleration? Less than 20 rad/s/s Between 20 and 40 rad/s/s Between 40 and 60 rad/s/s Between 60 and 80 rad/s/s More than 80 rad/s/s
between 60 and 80 rad/s/s
intrinsic injury factors
body weight (can be +or -), skeletal density, alignment, and asymmetry, Muscular strength, endurance, and firing pattern, previous injury and psychological factors such as motivaition and pain tolerance
Pressure vs stress
both pressure and stress= F/A, measured in N/M2, or Pa. Stress is the internal resistance a material offers to deformation. It is measured as force divided by area.
how can cyclists conserve up to 27% of energy when riding
by drafting off another cyclist. This is possible due to decreased drag forces that occur behind the lead cyclist who creates a lower velocity and pressure of air in front of the cyclist who is drafting.
Centrifugal accelration occurs when centripetal acceleration is generated due to which of Newton's Laws of Motion? A: 1st B: 2nd C: 3rd D: 4th
c 3rd
Angular inertia depends upon: A: Only mass B: Position of the object C: Mass and mass distribution
c Mass and mass distribution
Terminal velocity requires... A: The sum of forces other than gravity are greater than gravity B: The sum of forces other than gravity a less than gravity C: The sum of all forces are in equilibrium D: The sum of all forces other than gravity are in equilibrium
c equilibrium
loading rate
change in force over change in time
Muscle activation occurs when _____________ flows into the intracellular space. A: Negatively charged Ca B: Positively charged Ca C: Negatively charged Na D: Positively charged Na
d NA+
Limitations of surface EMG measurements include A: Electrodes move with the skin rather than with motor units B: Signal loss occurs due to tissues between the muscle and electrodes C: In many areas, it is impossible to isolate just one muscle D: All of the above
d all
With increased elevation, air pressure tends to__, which causes__?
decrease, thus decreasing air density
What effect does increased altitude have on lift and drag forces at the beginning of the flight (if temperature and humidity remain the same)? The forces are decreased The forces are increased The forces remain the same
decreased decreased air pressure
when a runner flexes at the knee the radius of gyration of the hip is: increased decreased Which has what effect on the moment of inertia at the hip? why does this matter?
decreased/ decreases inertia is the resistance to a change in motion, decreasing the resistance by decreasing the radius of gyration allows runners to use less energy to run
as humidity increases, air density ___?
decreases because water vapor has a lower density than air.
As air temperature increases, fluid density __?
decreases due to faster moving particles, less molecules fit when they are more rapidly moving. air density tends to also decrease with increase elevation.
dynamic force
due to relative motion in a fluid. the forces acting on an object as it moves through a fluid are dynamic forces. The dynamic force is proportional to the density of the fluid, the surface area of the object, and the square of the relative velocity of the object with respect to the fluid. With relative velocity being a squared value, it is evident to see that its contribution is the most influential factor in avoiding or creating dynamic fluid forces. Relative velocity considers the velocity of the object with respect to the velocity of the fluid. Therefore, relative velocity is the vector subtraction of the objects velocity from the fluids velocity.
During a baseball pitch (the part when the arm is moving forwards), what is the joint action at the elbow? Flexion Extension Supination Pronation
extension
The fibula is more medial than the tibia. True False
false
Bernoulli's Principle
faster moving fluids exert less pressure laterally than slower moving fluids. faster moving fluids on one side will create lower pressure based upon shape differences.
Passive muscle force
force generated by the connective tissue that makes up the muscle (sarcolemma, endomysium, perimysium, epimysium, and muscle tendon). as external and internal forces are produced connective tissue may be deformed, resulting in passive muscle force caused by connective tissue.
Angular Kinetics
forces that influence angular motion
laminar flow
form drag when relative velocity is low, causes fluid molecules to stay close to the objects surface causing smooth parallel layers.
Frequency
frequency : The rate at which an event occurs, typically measured in Hertz (cycles per second). If some damage occurs with each impact without time for recovery, the damage is summed together and may lead to injury.
Stability
height of center of mass, size of base support and weight all affect stability. ability to return to equilibrium after being displaced. & ability to maintain equilibrium. Lower COM height and bigger BOS are more stable because a smaller torque on the body will be required. but increased weight makes it harder to return to eq after being displaced.
two ways to increase cross sectional area
hypertrophy- increase in muscle fiber size from training, can lead to increased force production. hyperplasia- proliferation of muscle cells
A 140-lb diver performs a 1 ½ flip off a diving board. While spinning 1220 deg/s, the diver has a radius of gyration of 0.3m. What is the angular momentum at this point?
Angular Momentum (kgm 2/s): 122 convert to rad!
form drag
influenced by the size and shape of an object. component of drag force created by the pressure difference between the front and back sides of an object. Form drag occurs when an fluid molecule first strikes an object, then bounces off of the object to strike another molecule. This collision then causes that original colliding molecule to be sent back towards the objects surface. As this continues, the fluid molecule then follows the curvature of the objects surface as it passes the object.
When knee flexion is increased (heel brought to buttocks) during running, the moment of inertia of the lower extremity about the hip is increased is decreased remains the same moment of inertia cannot be measured about the hip
is decreased
centripetal acceleration formula
is the acceleration directed towards the axis of rotation. It is equal to the angular velocity (ω) squared multiplied by the radius of rotation (r). The angular velocity must be entered in radians per second.
Consider the following situation. A 689 N person lies down on a 2-m, 30-N board. Their feet are exactly at the fulcrum. They are 1.75 m tall. The scale reads 330 N. Where is their center of mass relative to their feet? Less than 1.00m Between Between 1.00m & 1.10m Between 1.10m & 1.20m More than 1.20m
less than 1m
Angular momentum will be conserved in which of the following (ignore air resistance in this)? A: Giant swing in gymnastics B: A golf club during a swing C: A dive while airborne
C: A dive while airborne
What is tangential acceleration? A: The accleration towards the axis of rotation B: The acceleration away from the axis of rotation C: The acceleration in the direction of motion
C: The acceleration in the direction of motion
Calculating COM
Calculating the center of mass of any given object is completed by balancing the torques around the center of mass. for body calculations this requires knowledge of the distribution of mass with body segment parameters.
A 90-kg (including any equipment) skydiver drops out of a plane. Using an air density of 1.0 kg/m3, a frontal surface area of 1.0 m2, and a drag coefficient of 0.8, what will the skydiver's terminal velocity be? Less than 50 m/s Between 50 and 100 m/s Between 100 and 150 m/s More than 150 m/s
less than 50 remember that sin 90=1
two components of dynamic forces are:
lift force and drag force
actin myosin
myosin- The protein filaments that move along actin filaments to produce muscle force. actin- The thin filaments of muscle. Actin is a protein involved in coupling with muscle to produce force.
What would happen to the center of mass of the person if the board weighed twice as much? The person's center of mass would not change. The person's center of mass would go towards the scale. The person's center of mass would go towards the fulcrum.
no change
Yakovlev's model
observed the body's reactions to stresses and applied those reactions to appropriate training has to do with fatigue, work capacity, recovery and next training session
A person is trying to close a door by making a force F1 = 200 N at a distance d1= 0.83 m from the door hinge. Another person is trying to open the door by making a force F2 = 250 N at a distance d2 = 0.70 m from the door hinge. What will happen? The door will open. The door will close. The door will remain half open. The door will fall off its hinges.
opeeennnn
rom most influential to least, what is the order of how humidity, air pressure, and temperature determine air density? air pressure, temperature, humidity air pressure, humidity, temperature humidity, temperature, air pressure temperature, humidity, air pressure
pressure, temp, humidity
Which of the following combinations will increase stability? Increasing the height of the center of mass and keeping the size of the base of support the same. Decrease the height of the center of mass and increasing the base of support. Increasing the size of the base of support and increasing the height of the center of mass. Keeping weight the same and decreasing the size of the base of support.
Decrease the height of the center of mass and increasing the base of support.
During a forehand drive in tennis, what is the main joint action at the radioulna joint? Think of the hit as one where you are going for topspin. The hand and racquet rotate over the top of the ball. Flexion Extension Supination Pronation
pronation
If a net external force is applied to the body, an angular acceleration will result that is...
proportional to the object's moment of inertia.
neural factors of active muscle force production
recruitment patterns : The timing and amplitude of motor unit activation. recruitment rates :The frequency of the signal which is activating muscle. the amount of force that a muscle can produce depends on the number of motor units that are recruited and the rate at which those motor units are recruited. Recruitment patterns describe the number of motor units that can be stimulated (recruited) by the neural system. As the number of motor units that are recruited increases, the number of binding actin and myosin filaments increase, and the magnitude of active muscle force that is produced increases. It is believed that the magnitude of force that is required by the muscle affects the amount of recruitment that will occur. Also, it is generally accepted that various forms of athletic training, including resistance training, will result in more effective, or synchronized, recruitment of various motor units. In addition to this more effective motor recruitment, skeletal muscles also produce more force when more neural impulses are sent in a given amount of time. This also is believed to be affected by exercise.
two components that make up drag force are?
Form drag and surface drag
Anterior-posterior Axis- which plane corresponds?
Frontal Plane- think hip abd
Segment length percent
represent the location of each segment's center of mass, measured proximal to distal.
calculating CM for the body
requires the knowledge of mass and position of each part of the body. We have a mass and mass distribution table for males and females. measures segment length percents from proximal to distal.
pennated muscle fibers
run in a direction that is not parallel to the long axis. this affects force production capability because when active force is produced it is not directed towards the long axis In other words, the force that pennated muscle fibers produce is not the same magnitude of force that is produced along the long axis of the muscle fiber (or in direction of the line of pull). In order to calculate the force that is calculated along the line of pull, one must multiply the cosine of the angle of pennation by the force produced by the muscle fibers
lift force
second of the dynamic forces, acts perpendicular to the motion of a body through fluid. can act in any direction, not just up. does not hinder the relative motion, but changes the direction of the motion. occurs due to bernoullis principle. A is total surface area velocity is relative, squared
One factor that affects force production capability is is the arrangement of the actin and myosin filaments, within the muscle fibers. two arrangements are: describe each
series and parallel series- fasicles are end to end along the long axis of a muscle. Although this arrangement is not most beneficial when it comes to force production, this arrangement does facilitate movement throughout a larger range of motion; longer muscle fibers maintain larger ranges of motion. parallel- fasicles are side to side. force production capability is maximized under the parallel arrangement; however, the parallel arrangement is not as conducive to range of motion as the series arrangement. As the number of parallel muscle fibers increase, force production capability also increases. In other words, muscles don't get stronger by becoming longer. They become stronger by becoming wider, or thicker.
What would happen to the scale's measure if someone with a high center of mass, but equal weight to someone else were placed on the board? It would show a greater weight. It would show a lower weight. It would not change.
show a greater weight
Muscle fiber type affects the magnitude of force that can be produced by skeletal muscle, as well as the rate of force production. Generally, muscle fibers a classified into one of four categories: most powerful and why?
slow twitch fatigue resistant : Type (I) A muscle fiber type with a low activation frequency, but a relatively long time to fatigue. fast twitch fatigue resistant : Type (IIa) A muscle fiber type with a activation frequency greater than type I fibers and a relatively long time to fatigue. faster twitch fatigue resistant : (Type IIx) A muscle fiber type with a activation frequency greater than type IIa fibers and a relatively long time to fatigue. fastest twitch fast fatigue : Type (IIb) A muscle fiber type with the greatest activation frequency and a fast time to fatigue. Related to these categories, the power capability is least for the Type I muscle fibers, and greatest for the Type IIb muscle fibers, while the Type IIa and IIx fibers are capable of producing intermediary magnitudes of power. It is generally believed that the ability of the fast twitch muscle fibers to produce more force is due to their high contraction rates
Name two ways to determine if an object will float
specific gravity and density
For most joints of the body, the lever system is designed for: Speed Strength Endurance Smaller ranges of motion
speed
how to decrease form drag
streamline (gradually curve) the surface to decrease turbulent flow. even at low velocities a non-smooth surface causes more turbulent flow.
If someone were able to lengthen the radius of the hammer without losing angular velocity, what would happen to the linear velocity? It would not change It would increase It would decrease
It would increase
optimal fiber length
the basis for active muscle force production is the attachment of the myosin cross bridges to the actin filaments, there is an optimal fiber length in producing skeletal muscle force. That length is the length that optimizes the myosin head overlap with the actin filaments, and this length is sometimes called the sarcomere resting length. Relative to this resting length, as the sarcomere shortens, the actin filaments may begin to overlap. For a reason that is not well understood, the myosin cross bridges do not appear to be able to attach to these overlapping actin filaments; therefore, the force production decreases. Furthermore, as the sarcomere continues to shorten, the actin and myosin filaments begin to bump into the Z-lines and additional force cannot be produced; this has been estimated to be somewhere around 60% of resting sarcomere length. Conversely, if the sarcomere lengthens beyond the resting sarcomere length, the actin myosin overlap is decreased and force production capabilities are also decreased. At some point during the lengthening process, no more actin myosin overlap occurs and the muscle is no longer able to produce active muscle force; this has been hypothesized to be somewhere near 160% of the sarcomere resting length.
why are golf balls special when it comes to form drag?
the dimples cause a layer of turbulent flow to be trapped by the ball and move with the ball. the remaining fluid follows laminar flow, which does not have as much drag, thus increasing distance.
Magnus effect magnus force
the lift force created by pressure differences on one side of a spinning round object relative to another side the lift force created by a spinning object
some joint motions in the TRANSVERSE PLANE/LONGITUDINAL AXIS
Shoulder Internal Rotation Shoulder External Rotation Shoulder horizontal abduction Shoulder horizontal adduction Hip Internal Rotation Hip External Rotation Radio/ulnar pronation Radio/ulnar supination Trunk rotation Neck rotation
specific gravity
Specific gravity is one way to determine if an object will float. Specific gravity is defined as the weight of an object divided by the weight of an equal volume of water. If the specific gravity is 1.0 or less, that object will float.
Part of the ability for many distance runners to move fast with good economy deals with:
the mass distribution of the lower leg (tapered) and using optimal angles of knee flexion, etc, to decrease radius of gyration and moment of inertia, and allow good push off/ acceleration
Movement arm / Lever arm
the perpendicular distance from the axis of rotation and where the force is applied (line of force).
Young's Modulus
the ratio of stress to strain in Pa (N/m2) it is a measure that describes the stiffness or compliance of a biological structure. Young's Modulus indicates how much force is required to deform a biological structure. Young's Modulus equals the slope of the stress-strain curve. A steep stress-strain curve indicates a stiff structure, while a more gradual stress-strain curve indicates a more compliant structure.
surface drag also known as? influenced by?
the second component of drag force that is influenced by the interaction of the surface of the object and the molecules of the fluid that it is passing through. occurs when a fluid molecule slides past the surface of an object. the friction produced causes the fluid molecule to decrease in speed, which then slows down the surrounding molecules, and so on. also known as skin friction or viscous drag influenced by drag force equation components and viscosity of the fluid, and surface texture of the object.
Most biological structures, including bones, muscles, tendons, and ligaments, are anisotropic, meaning:
the stress-strain characteristics differ, depending on the stress direction. Bones, muscles, tendons, and ligaments respond differently to different kinds of stress
When a ball has top spin, what happens?
the top side of the ball slows down the fluid coming into contact with it while the bottom side either speeds it up or at least does not slow it down at much. This leads to a faster moving fluid on the bottom of the ball compared with the top. Remembering Bernoulli's principle that high velocity fluids produces a low pressure area, and low velocity fluids produce a high pressure area, the pressure on the top side of the ball is higher than the pressure on the bottom side. This difference in pressure results in a Magnus force acting in the high to low pressure direction, pushing the tennis ball downward. A simpler way to think about the Magnus effect is to think of the direction of the spin on the ball. The Magnus force causes the path of the object to deviate in the direction of the spin
H=Iw
think back to linear kinetics and linear momentum - a concept that allows us to examine the effects of mass and velocity together. Angular moments are calculated using the angular equivalents to mass and velocity - moment of inertia and angular velocity. Therefore, it is also influenced by the mass of the object, the distribution of the mass, and the velocity at which the object rotates . in radians/sec!!
Angular impulse is the product of: force and the time that force is applied torque and the time that torque is applied angular inertia and angular momentum mass and angular velocity force and torque
torque and the time that torque is applied
Which area should the area be calculated when determining lift force? Frontal Top Bottom Total Surface Area Side
total surface area
Centripetal acceleration (spinning figure skater) is the acceleration directed... away from the axis of rotation towards the axis of rotation along the axis of rotation Parallel to the axis of rotation None of the above
towards the axis of rotation
The plane that splits the body into superior and inferior halves.
transverse plane :
Once a high jumper leaves the ground, she cannot change the path of her center of mass (relative to some fixed reference point on the ground). True False
true
form drag is influenced by?
turbulent flow- as the amount of turbulent flow increases, the amount of form drag increases. the surface texture of the object factors in the drag force equation
Ulnar vs radial deviation
ulnar is pinky towards wrist, radial is thumb towards wrist.
