Lecture #2 (Forces & Tissue Properties) Flashcards

1
Q

What is the definition of force?

A

That which pushes or pulls through direct mechanical contact or through the force of gravity to alter the motion of an object.

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2
Q

What are internal forces?

A

Forces that act on various structures of the body (i.e. muscle forces)

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3
Q

What are external forces?

A

Forces that are outside the body (i.e. weight, gravity, air/water resistance, friction, other objects, etc.)

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4
Q

What type of quantity is force?

A

A vector

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5
Q

What does a vector force have? (3)

A

Magnitude
Direction
Point of application

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6
Q

True or false:

Gravity has a point of application.

A

False–gravity is a constant force, therefore it does not have a point of application.

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7
Q

What type of movement has no effort on the part of the subject involved, and the motion is completely due to an outside force?

A

Passive

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8
Q

What type of movement is produced by the subject’s own muscular activity?

A

Active

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9
Q

How it the human body designed to move? Why?

A

The human body is made for bursts of movement and sustained momentum rather than slow movements. This is because it takes less energy for us to do so.

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10
Q

What is the imaginary point representing the weight center of an object?

A

Center of gravity (COG)

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11
Q

Where is our COG?

A

Anterior to S2

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12
Q

True or false:

Males have a slightly lower center of gravity than women.

A

False

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13
Q

What is the imaginary vertical line that passes through the center of gravity (the action line and direction of force of gravity on a person)?

A

Line of gravity (LOG)

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14
Q

When does a person fall over?

A

When their line of gravity gets outside the base

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15
Q

What type of forces cause movement?

A

Unbalanced forces (if the forces were balanced, then no movement would happen because of a net force of 0)

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16
Q

What type of force occurs within the body? Outside the body?

A

Internal; external

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17
Q

What type of force is produced by muscular activity?

A

Internal

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18
Q

What is an example of a constant, external force?

A

Gravity

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19
Q

What is the magnitude of a force?

A

The amount of force being applied (the power behind the force)

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20
Q

What is weight? (formula)

A

Mass x acceleration due to gravity

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21
Q

True or false:

Muscles can create various magnitudes of force to create, halt, and control motion.

A

True (this is why kids can be uncoordinated)

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22
Q

How does force occur in the body?

A

In direct proportion to the number and size of fibers contracting in the muscle (typically measured in groups of muscles)

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23
Q

How do forces work in the body?

A

They go through a lever system (skeletal system)

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24
Q

How do you want your base of support?

A

As wide a possible

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25
Q

What is the point of application?

A

The point at which a force is applied to an object

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26
Q

Where does gravity have its point of application? For a muscle?

A

COG; the muscle’s attachment to a bony lever (point of intersection of the line of force and the mechanical axis of the bone)

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27
Q

Provide an example of a scenario in which there is multiple forces applied to the same object.

A

A punted ball (force of kick, gravity, and wind)

Quadriceps contracting

28
Q

What are colinear forces?

A

Forces that are applied in a straight line with the result being the sum of the forces (a+b=c) or (a+ -b=c)

29
Q

What are concurrent forces?

A

Forces that act at the same point of application at different angles

30
Q

What are parallel forces?

A

Forces that are parallel to each other but not in the same action line.

31
Q

True or false:

Everything provides a parallel force against gravity.

A

True

32
Q

What is friction?

A

The force that opposes efforts to slide or roll one body over another

33
Q

What does the amount of friction depend on?

A

The nature of the surfaces and the forces pressing them together

34
Q

What is an example of an anatomical structure that helps to work against friction?

A

Bursa sacs

35
Q

How does the force of friction work when compared to the object?

A

Parallel to surfaces and opposite to the direction of motion

36
Q

True or false:

The force generated by muscle may be summated from one segment to another

A

True–this is how motion in sports happens (think of throwing as an example- the forces from legs is transferred to the trunk and so on)

37
Q

What is the resolution of external forces?

A

It is accomplished in the same manner as muscular forces applied at an oblique angle (so we have to position ourselves to get the best possible use of force)

38
Q

What is the force of gravity measured as the weight of the body applied through the COG of the body and directed towards the earth’s axis?

A

Weight

39
Q

What is the ability to resist distorting influences and to return to the original size and shape?

A

Elasticity

40
Q

In regards to elasticity of muscle, what acts to distort it and what is the distortion that occurs?

A

Stress=acts to distort

Strain=distortion that occurs

41
Q

What type of force occurs when the direction of force is not in line with the object’s COG?

A

Rotary force

42
Q

What is torque?

A

The force it takes to create rotation

43
Q

What type of equilibrium occurs when an object is placed in such a way that an effort to disturb it would require it’s COG to be raised?

A

Stable (because it has a lower COG)

44
Q

What type of equilibrium occurs when a slight disturbance will drop the subjects COG to a lower point?

A

Unstable (because it has a higher COG)

45
Q

What type of equilibrium occurs when an object’s COG is neither raised nor lowered when it is disturbed?

A

Neutral

46
Q

How is stability maintained?

A

When external forces = internal forces

47
Q

What type of force causes stability? Instability?

A
Stability= internal forces
Instability= external forces
48
Q

What is the force that pulls and stretches tissue? WHat creates it?

A

Tension (what muscles create)

49
Q

What is the force that pushes tissues together that may result in their crushing?

A

Compression

50
Q

What is the force that moves across the parallel organization of tissue?

A

Shearing

51
Q

What is the force that acts on a horizontal beam that places stress within the structure?

A

Bending

52
Q

What is the force that causes an unaxial stress or twist of tissue?

A

Torsion

53
Q

What types of forces are catastrophic in nature?

A

Shearing, bending, and torsion

54
Q

What types of injuries do shear forces cause? (x6)

A
Spondylolisthesis
Disc herniations
SI joint pain
Spiral fractures
Meniscal/labral tears
Blisters
55
Q

True or false:

Our bodies are visoelastic and contain both viscous and elastic properties.

A

True

56
Q

What is the yield point?

A

The point at which elasticity is almost exceeded

57
Q

What does the stress/strain curve depict?

A

The stresses vs strain of a material (i.e. the amount of deformation that can occur)

58
Q

Of the distinct regions of loading on the stress/strain curve, which is when the tissue stretches easily without much force? (Making the fibers go from wavy to straight)?

A

Toe region

59
Q

Of the distinct regions of loading on the stress/strain curve, which is when there is continue stress added to the tissue–but more force is still needed to create further deformation?

A

Elastic region

60
Q

Of the distinct regions of loading on the stress/strain curve, which is the transition from the elastic region to the plastic region?

A

Yield point

61
Q

Of the distinct regions of loading on the stress/strain curve, which is when the load has resulted in a stretch beyond the tissue’s ability to return to pre-load length? (there are microscopic tears occuring here)

A

Plastic region

62
Q

Of the distinct regions of loading on the stress/strain curve, which is when the load and rate have exceeded the mechanical properties of tissue?

A

Region of failure

63
Q

What is the slope of the stress/strain curve?

A

Young’s modulus

64
Q

What is the area under the stress/strain curve?

A

Toughness (resistance to force)

65
Q

What occurs with low load, short duration?

A

Hysteresis