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102 Cards in this Set
- Front
- Back
Why study biomechanics? |
1) Improve health 2) Reduce risk of injury 3) Improve performance |
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dorsiflexion |
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Retus femoris |
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15N |
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63.58 N |
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Do tan-1 (Fy/Fx) |
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What is the equation for Newton's 2nd Law? |
sigma F = m *a |
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Linear motion is motion of ______ point |
a single |
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B |
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What is the equation for velocity? |
Displacement/time |
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Is velocity a vector or scalar? |
Vector |
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What is the equation for speed? |
Distance/ time |
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Is speed a vector or scalar? |
Scalar |
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4-1/total time |
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A |
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Acceleration is a change in ____ over ______ |
*Velocity (or speed) *Time |
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Can an acceleration be either a vector or scalar? |
It can be either |
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When you are moving your leg, what kind of acceleration do you have? |
A forward and vertical acceleration |
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How do you find "instantaneous" velocity from a graph? |
From the line slope |
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Is an "instantaneous" velocity truly "instant" |
No |
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How do you find the derivative of a graph? |
Take the slope |
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How do you find the integral of a graph? |
Take the area under the curve |
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Central Difference Method |
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For projectile motions, what are the equations for a constant acceleration? |
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What angular componenet of postiion? |
Degrees or radians |
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What is the angualr velocity? |
(omega symbol)
rad/s |
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What is the angular acceleration |
rad/s^2
(alpha symbol) |
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What is the distance?
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95 degrees |
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What is the displacement
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45 degrees |
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What is s stand for?
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arc of motion
(Also used for linear position) |
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How do you get to S from θ? |
S = θ * r
(θ = distance change) |
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What is the relationship between velocity and angular velocity? |
v = ω * r |
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What is the relationship between acceleration and angular acceleration |
a = α * r |
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What is the foot displacement?
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(62°) ( pi/180 °) = 1.082104136 rad
(1.08...)(50 cm)
= 54.10520681 cm |
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How many steps is each stride made up of? |
2 steps |
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How long are most people's shanks? |
30-40 cm |
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(62 °) (pi/180 °) = 1.082104136 rad
(1.08...rad) (50 cm) = 54.105 cm
54.105 cm/ 0.01 s
= 5410 cm/s |
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Is there still linear acceleration even when angular velocity is constant? |
Yes |
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What is the equation for tangenital acceleration? |
A(t) = α * r |
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What is the equation for centripetal/normal/radial acceleration? |
a (N) = r * ω^2 |
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Since the tangenital acceleration and centripetal acceleration are othogonal, the magnitude of the resultant linear acceleration can be found by how? |
Pythagorean Theorem
a= √ (at^2 + ac^2) |
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What other terms can you calcualte the resultant linear acceleration in? |
Energy terms |
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Find Knee angle (clinical) |
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What are relative angles? |
Joint angles
The angle between the longitudinal axis of two adjacent segments (Angle between one segment and another)
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What are absolute angles? |
(Segment angles)
The angle between a segment and the right horizontal of the distal end (with respect to some common reference)
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How many degrees is anatomical postion of clinical angles? |
Zero degrees |
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What is clinical angles? |
There is a neutral reference
(Knee referenced with respect to the thigh; hip referenced with respect to the thigh) |
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What is a "body" in terms of a system? |
Any object (animate or inanimate) |
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What is a "rigid body" of a system? |
A body whose shape and size are not influenced by external forces
Not going to change; assume bony structure not changing, some error because of outside will move it a little bit) |
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What is a force? |
1) A push or pull that results from physical contact between two objects with the exception of gravity
2) Any action that tends to change the state of rest or state of motion of the body to which it is applied |
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What are the primary effector of change in a human body? |
Muscles |
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Do muscles actively extend? |
No |
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What muscle is responsible for a push/ |
Push happens because the muscle is affecting joint system because of tension |
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32.14 N |
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what are the types offorces? |
1) Gravity 2) soft tissues 3) Friction 4) Contact 5) Inertia |
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What is gravity force? |
Weight (vs mass) |
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What is soft tissues forces |
Muscles and ligaments |
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What is friction forces? |
heat (caused by friction) |
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What is contact forces? |
Joint reaction Ground reaction Friction |
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What is inertia forces? |
Acceleration |
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Friction is contact between what? |
2 objects (sheer forces gives way to friction) |
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What is coulomb friction? |
Dry friction, almost not even possible |
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What is fluid friction? |
Lubriction (think cartilage)
Sheer , compressive |
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What is μ(s)? |
Coefficient of static friction |
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What is the frictional force that will match the applied force so that the box will not move as long as F < Fmax (what is the equation to find F max)? |
μ(s) * N |
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The Normal force is ______ to the weight vector |
Equal and opposite |
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During toe off what direction is the action in and what direction the friction |
Action: ← Friction: → |
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During heel strike, what is the direction of action and friction? |
Action: → Friction: ← |
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F Fr = (0.4)(900) = 360
(This is the max force that static friction can go against)
However, this is less than horizontal force, so therefore that has overwhelmed the frictional force and so the slip WILL occur |
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What generates forces in our bodies? |
Muscles |
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What is an internal force? |
Acting within the body of interest |
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What is an external force? |
Actingo n the body of interest |
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Are internal and external forces going against each other? |
Yes |
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1793.2 N |
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84.4 degrees |
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F = 1686 N
(Find orientation also) |
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Forces result in:
A) Rotations only B) Translation only C) Both D) None |
C
Can only know when know where the fixed axis is
(If off center will be a rotation, if in the middle will cause a translation) |
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Forces tend to cause ____ |
Translations |
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Moments tend to cause _____ |
Rotations |
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What will this force cause?
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Tend to rotate to plantarflex |
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What is a tendon that can cause plantarflexion? |
Achilles tendon |
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What thre numbers do you need to calculate moment or torque? |
Force (from where muscle inserts) --> Beginning of force vector is the origin or insertion point
T = F * d * sin (θ) |
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The shortest perpendicular distance between the force vector and the center of rotation |
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F1 = 500 N d1 = 8 cm θ1 = 60°
F2 = 600 N d2 = 7 cm θ2 = 45°
What is the net torque |
T1 = (500)(0.08)(sin (60)) T2= - (600)(0.07)(sin (45))
Net torque = T1 + T2 |
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What can the gastrocnemius do? |
Plantarflex Dorsiflex |
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What is the methods for increasing torque? |
*Alter angle *Alter distance *Alter force
(Increasing any of these will increase torque)
*If recruit greater power will increase torque
*Increasing distances will increase the force W |
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What are the force couples? |
Two forces acting on a body that:
-Are parallel -Are equal in magnitude, but opposite in direction -Have equal moment arms
Idealized:
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(Not drawn to scale) |
They have equal moment arms but the deltoid has greater forces so therefore has a higher torque |
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What are the limitations of the points of reference? |
*Direction (muscle force can only have on direction [tension])
*Orientaiton and point of application (Can be measured from cadavers r imaging techniques such as MRI and CT)
*Magnitude (The magnitude of force of tension is derived by cross sectional area IE if there is a decreased cross sectional area, there is less force) |
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-10.14 N*m
Quads win
(The prof put hamstring as "negative) |
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What do the forces and moments sum to in static equilibrium? |
Zero |
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What is the velocity equal to during static equilibrium? |
Zero |
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? |
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What does Newton's 1st Law state? |
An object will remain at rest (or continue moving at a constant velocity) unless acted upon by an unbalanced external force.
Static equilibrium = sum of forces and moments = 0 |
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What is Newton's 2nd Law? |
If there is an unbalanced force acting on a object, it will produce an acceleration in the direction of the force, directly proportional to the force (f = ma)
Reduces to 1st law when a = 0 |
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What does Newton's 3rd Law state? |
For every action (force) there is a reaction (opposing force) of equal magnitude but in the opposite direction
Important for all constant forces
Anything that happens has a reaction |
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What static equilibrium equations do you have for 3D analysis? |
1) ΣFx = 0 2) ΣFy=0 3) ΣFz = 0 4) ΣMx = 0 5) ΣMy =0 6) ΣMz=0 |
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What static equilibirum equations do you use for 2D analysis? |
1) ΣFx = 0 2) ΣFy=0 3) ΣMz = 0 |
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How do you model problems? |
1) Isolate the body of interest 2) Sketch as a simple figure, this body and all external forces 3) Sum the forces and moments equal to zero 4) Solve for unknown forces (and moments) |
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T = 20 N
(Solved in Week 3-2 P. 4) |
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Most joints behave as ____ class levers |
3rd |
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In general, muscle forces are _____ than the resistive load |
greater |