Biomechanics Midterm 1

Front 1

Why study biomechanics?

Back 1

1) Improve health

2) Reduce risk of injury

3) Improve performance

Front 2

Back 2

dorsiflexion

Front 3

Back 3

Retus femoris

Front 4

Back 4

15N

Front 5

Back 5

63.58 N

Front 6

Back 6

Do tan-1 (Fy/Fx)

Front 7

What is the equation for Newton's 2nd Law?

Back 7

sigma F = m *a

Front 8

Linear motion is motion of ______ point

Back 8

a single

Front 9

Back 9

B

Front 10

What is the equation for velocity?

Back 10

Displacement/time

Front 11

Is velocity a vector or scalar?

Back 11

Vector

Front 12

What is the equation for speed?

Back 12

Distance/ time

Front 13

Is speed a vector or scalar?

Back 13

Scalar

Front 14

Back 14

4-1/total time

Front 15

Back 15

A

Front 16

Acceleration is a change in ____ over ______

Back 16

*Velocity (or speed)

*Time

Front 17

Can an acceleration be either a vector or scalar?

Back 17

It can be either

Front 18

When you are moving your leg, what kind of acceleration do you have?

Back 18

A forward and vertical acceleration

Front 19

How do you find "instantaneous" velocity from a graph?

Back 19

From the line slope

Front 20

Is an "instantaneous" velocity truly "instant"

Back 20

No

Front 21

How do you find the derivative of a graph?

Back 21

Take the slope

Front 22

How do you find the integral of a graph?

Back 22

Take the area under the curve

Front 23

Central Difference Method

Back 23

Front 24

For projectile motions, what are the equations for a constant acceleration?

Back 24

Front 25

What angular componenet of postiion?

Back 25

Degrees or radians

Front 26

What is the angualr velocity?

Back 26

(omega symbol)

rad/s

Front 27

What is the angular acceleration

Back 27

rad/s^2

(alpha symbol)

Front 28

What is the distance?

Back 28

95 degrees

Front 29

What is the displacement

Back 29

45 degrees

Front 30

What is s stand for?

Back 30

arc of motion

(Also used for linear position)

Front 31

How do you get to S from θ?

Back 31

S = θ * r

(θ = distance change)

Front 32

What is the relationship between velocity and angular velocity?

Back 32

v = ω * r

Front 33

What is the relationship between acceleration and angular acceleration

Back 33

a = α * r

Front 34

What is the foot displacement?

Back 34

(62°) ( pi/180 °) = 1.082104136 rad

(1.08...)(50 cm)

= 54.10520681 cm

Front 35

How many steps is each stride made up of?

Back 35

2 steps

Front 36

How long are most people's shanks?

Back 36

30-40 cm

Front 37

Back 37

(62 °) (pi/180 °) = 1.082104136 rad

(1.08...rad) (50 cm) = 54.105 cm

54.105 cm/ 0.01 s

= 5410 cm/s

Front 38

Is there still linear acceleration even when angular velocity is constant?

Back 38

Yes

Front 39

What is the equation for tangenital acceleration?

Back 39

A(t) = α * r

Front 40

What is the equation for centripetal/normal/radial acceleration?

Back 40

a (N) = r * ω^2

Front 41

Since the tangenital acceleration and centripetal acceleration are othogonal, the magnitude of the resultant linear acceleration can be found by how?

Back 41

Pythagorean Theorem

a= √ (at^2 + ac^2)

Front 42

What other terms can you calcualte the resultant linear acceleration in?

Back 42

Energy terms

Front 43

Back 43

Find Knee angle (clinical)

Front 44

What are relative angles?

Back 44

Joint angles

The angle between the longitudinal axis of two adjacent segments (Angle between one segment and another)

Front 45

What are absolute angles?

Back 45

(Segment angles)

The angle between a segment and the right horizontal of the distal end (with respect to some common reference)

Front 46

How many degrees is anatomical postion of clinical angles?

Back 46

Zero degrees

Front 47

What is clinical angles?

Back 47

There is a neutral reference

(Knee referenced with respect to the thigh; hip referenced with respect to the thigh)

Front 48

What is a "body" in terms of a system?

Back 48

Any object (animate or inanimate)

Front 49

What is a "rigid body" of a system?

Back 49

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)

Front 50

What is a force?

Back 50

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

Front 51

What are the primary effector of change in a human body?

Back 51

Muscles

Front 52

Do muscles actively extend?

Back 52

No

Front 53

What muscle is responsible for a push/

Back 53

Push happens because the muscle is affecting joint system because of tension

Front 54

Back 54

32.14 N

Front 55

what are the types offorces?

Back 55

1) Gravity

2) soft tissues

3) Friction

4) Contact

5) Inertia

Front 56

What is gravity force?

Back 56

Weight (vs mass)

Front 57

What is soft tissues forces

Back 57

Muscles and ligaments

Front 58

What is friction forces?

Back 58

heat (caused by friction)

Front 59

What is contact forces?

Back 59

Joint reaction

Ground reaction

Friction

Front 60

What is inertia forces?

Back 60

Acceleration

Front 61

Friction is contact between what?

Back 61

2 objects (sheer forces gives way to friction)

Front 62

What is coulomb friction?

Back 62

Dry friction, almost not even possible

Front 63

What is fluid friction?

Back 63

Lubriction (think cartilage)

Sheer , compressive

Front 64

What is μ(s)?

Back 64

Coefficient of static friction

Front 65

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)?

Back 65

μ(s) * N

Front 66

The Normal force is ______ to the weight vector

Back 66

Equal and opposite

Front 67

During toe off what direction is the action in and what direction the friction

Back 67

Action: ←

Friction: →

Front 68

During heel strike, what is the direction of action and friction?

Back 68

Action: →

Friction: ←

Front 69

Back 69

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

Front 70

What generates forces in our bodies?

Back 70

Muscles

Front 71

What is an internal force?

Back 71

Acting within the body of interest

Front 72

What is an external force?

Back 72

Actingo n the body of interest

Front 73

Are internal and external forces going against each other?

Back 73

Yes

Front 74

Back 74

1793.2 N

Front 75

Back 75

84.4 degrees

Front 76

Back 76

F = 1686 N

(Find orientation also)

Front 77

Forces result in:

A) Rotations only

B) Translation only

C) Both

D) None

Back 77

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)

Front 78

Forces tend to cause ____

Back 78

Translations

Front 79

Moments tend to cause _____

Back 79

Rotations

Front 80

What will this force cause?

Back 80

Tend to rotate to plantarflex

Front 81

What is a tendon that can cause plantarflexion?

Back 81

Achilles tendon

Front 82

What thre numbers do you need to calculate moment or torque?

Back 82

Force (from where muscle inserts) --> Beginning of force vector is the origin or insertion point

T = F * d * sin (θ)

Front 83

Back 83

The shortest perpendicular distance between the force vector and the center of rotation

Front 84

F1 = 500 N

d1 = 8 cm

θ1 = 60°

F2 = 600 N

d2 = 7 cm

θ2 = 45°

What is the net torque

Back 84

T1 = (500)(0.08)(sin (60))

T2= - (600)(0.07)(sin (45))

Net torque = T1 + T2

Front 85

What can the gastrocnemius do?

Back 85

Plantarflex

Dorsiflex

Front 86

What is the methods for increasing torque?

Back 86

*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

Front 87

What are the force couples?

Back 87

Two forces acting on a body that:

-Are parallel

-Are equal in magnitude, but opposite in direction

-Have equal moment arms

Idealized:

Front 88

(Not drawn to scale)

Back 88

They have equal moment arms but the deltoid has greater forces so therefore has a higher torque

Front 89

What are the limitations of the points of reference?

Back 89

*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)

Front 90

Back 90

-10.14 N*m

Quads win

(The prof put hamstring as "negative)

Front 91

What do the forces and moments sum to in static equilibrium?

Back 91

Zero

Front 92

What is the velocity equal to during static equilibrium?

Back 92

Zero

Front 93

Back 93

?

Front 94

What does Newton's 1st Law state?

Back 94

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

Front 95

What is Newton's 2nd Law?

Back 95

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

Front 96

What does Newton's 3rd Law state?

Back 96

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

Front 97

What static equilibrium equations do you have for 3D analysis?

Back 97

1) ΣFx = 0

2) ΣFy=0

3) ΣFz = 0

4) ΣMx = 0

5) ΣMy =0

6) ΣMz=0

Front 98

What static equilibirum equations do you use for 2D analysis?

Back 98

1) ΣFx = 0

2) ΣFy=0

3) ΣMz = 0

Front 99

How do you model problems?

Back 99

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)

Front 100

Back 100

T = 20 N

(Solved in Week 3-2 P. 4)

Front 101

Most joints behave as ____ class levers

Back 101

3rd

Front 102

In general, muscle forces are _____ than the resistive load

Back 102

greater