Deck 13: Equilibrium and Human Movement

Question 1

In analyzing the human body as a projectile, which of the following quantities follows a parabolic path?

A) the center of mass
B) the center of volume
C) the navel
D) this varies with the individual performance

Answer 1

the center of mass

Question 2

Which of the following must be true for an object to be in a state of static equilibrium?

A) the sum of all vertical forces acting on the object must be equal to zero
B) the sum of all horizontal forces acting on the object must be equal to zero
C) the sum of all torques acting on the object must be equal to zero
D) all of the above must be true

Answer 2

all of the above must be true

Question 3

When a muscle contracts at a joint, which of the following affects torque?

A) the rotary component of muscle force
B) the stabilizing component of muscle force
C) the dislocating component of muscle force
D) none of the above

Answer 3

the rotary component of muscle force

Question 4

Which of the following factors influences the amount of torque produced by muscles at a joint?

A) the amounts of tension generated by the muscles
B) the arrangement of the muscles around the joint
C) both A and B
D) neither A nor B

Question 5

The amount of torque which must by generated by the biceps brachii at the elbow in order to maintain the arm in a particular position is 50 Nm. If the biceps attaches to the radius at a perpendicular distance of 3 cm from the joint center at the elbow, how much force must the muscle produce?

A) 1667 N
B) 17 N
C) 150 N
D) 1.5 N

Question 6

The perpendicular distance between the line of force and the axis defines what?

A) torque
B) fulcrum
C) moment arm
D) none of the above

Question 7

Which of the following is a characteristic of torque?

A) it is a vector quantity
B) it is characterized by magnitude
C) it is characterized by direction
D) all of the above

Question 8

A 30 kg child sits on the right end of a see-saw 1 m from the axis. If a 20 kg child sits on the left end of the see-saw 2 m from the axis, what will happen?

A) the see-saw will tilt to the right
B) the see-saw will tilt to the left
C) the see-saw will balance
D) need more information to predict outcome

Question 9

When the elbow is extended and the elbow flexors contract, which of the component forces acts in addition to the rotary component?

A) the stabilizing component of muscle force
B) the dislocating component of muscle force
C) both A & B
D) none of the above

Question 10

A seesaw is an example of which class of lever?

A) 1^st class
B) 2^nd class
C) 3^rd class
D) not a lever

Question 11

In the human body, most of the lever systems formed by muscles pulling on bones are what class?

A) 1^st class
B) 2^nd class
C) 3^rd class
D) no particular class is dominant

Question 12

Which of the following affects the force-generating capability of a muscle?

A) the muscle length and cross-sectional area
B) the angle and distance from the joint center of the tendon attachment to bone
C) the velocity of muscle shortening
D) all of the above

Question 13

The resistance arm (RA) will always be longer than the force arm (FA) in what class lever?

A) 1^st class
B) 2^nd class
C) 3^rd class
D) none of the above

Question 14

A wheelbarrow is an example of which class of lever?

A) 1^st class
B) 2^nd class
C) 3^rd class
D) not a lever

Question 15

Which of the following will improve leverage?

A) increase force arm
B) decrease resistance arm
C) both A & B
D) none of the above

Question 16

Which of the following does not increase stability?

A) lower the COG
B) increase size of base of support
C) decrease mass
D) increase friction

Question 17

A claw-tooth hammer being used to pry up a nail is an example of which class of lever?

A) 1^st class
B) 2^nd class
C) 3^rd class
D) not a lever

Question 18

Torque is the angular analogue of what?

A) momentum
B) force
C) mass
D) impulse

Question 19

Third class lever systems favor which of the following?

A) speed
B) range of motion
C) strength
D) both A and B
E) all of the above

Question 20

The relative efficiency of a lever is proportional to which of the following?

A) mechanical advantage of the lever
B) length of the force arm
C) length of the resistance arm
D) the amount of force needed to move the lever

Question 21

When net muscle torque and joint movement occur in the same direction, what type of contraction occurs?

A) concentric
B) eccentric
C) isometric
D) isotonic

Question 22

Which of the following is/are true regarding dynamic equilibrium?

A) applies to bodies in motion
B) first identified by D'Alembert
C) both A and B
D) there is no such thing as dynamic equilibrium

Question 23

Which of the following will benefit mobility?

A) increase mass
B) increase base of support
C) increase friction
D) raise center of gravity

Question 24

Which of the following is/are true regarding a force couple?

A) created by equal forces on opposite sides of an axis
B) created by forces acting in the same angular direction
C) both A and B
D) none of the above

Question 25

Which one of the following incorrectly identifies the parts of a lever within the human body?

A) a bone is the rigid bar
B) a joint is the axis of rotation
C) a muscle insertion provides the point of force
D) COM of the moving segment is the point of resistance
E) all of the above are correct

Question 26

Which of the following is/are true regarding center of mass?

A) in a spherical ball with evenly distributed mass, it is in the exact center
B) it is the point around which a body's weight is equally balanced regardless of body position
C) it may be located outside an object or body
D) both A and B
E) all of the above

Question 27

In which of the following situations is maximal stability desirable?

A) a swimmer's starting position on the blocks before a race
B) a Sumo wrestler's crouched defensive stance
C) both A and B
D) neither A nor B

Question 28

Which of the following phrases is/are synonymous with torque?

A) moment of force
B) rotary force
C) moment arm
D) both A and B
E) all of the above

Question 29

What is the importance of segmental center of mass to the lever systems of the human body?

A) segmental COM will follow a parabolic path when projected
B) segmental COM is the point of resistance (where weight vector is drawn) and therefore determines the length of the resistance arm
C) both A and B
D) none of the above

Question 30

Which of the following can increase base of support?

A) widen stance
B) add more points of contact (i.e. 3-point stance to 4-point stance)
C) both A and B
D) none of the above

Question 31

If disruption of stability is the desired outcome, which of the following should be observed?

A) lower COM
B) increase base of support
C) increase friction
D) move COM to edge of BOS

Question 32

The ability to control equilibrium defines what?

A) stability
B) balance
C) mobility
D) center of mass

Question 33

Which of the following is/are function(s) of antagonist muscles?

A) control velocity of movement
B) enhance stability of the joint
C) both A and B
D) none of the above

Question 34

Which statement is true regarding moment arm?

A) Moment arm is largest when the angle of pull on a bone is 90°.
B) Changes in moment arm directly affect joint muscle torque.
C) For torque to remain constant, more force must be produced when moment arm decreases.
D) both A and B
E) all of the above

Question 35

What is the proposed advantage of Nautilus resistance equipment over free weights?

A) resistance varies over the range of motion with Nautilus equipment
B) resistance varies over the range of motion with free weights
C) muscle force requirements change over the range of motion with Nautilus equipment
D) none of the above is advantageous

Question 36

Which of the following quantities is zero for an object in static equilibrium?

A) momentum
B) kinetic energy
C) both A and B
D) neither A nor B

Question 37

What will happen to the COM of a human body if the arms are raised up overhead?

A) it will move up
B) it will move down
C) it will not change
D) need more information to predict

Question 38

Which statement(s) is/are true regarding postural sway?

A) it affects balance in the elderly
B) it is reduced by widening the BOS to a certain point
C) it is increased by putting one foot in front of the other
D) both A and B
E) all of the above

Question 39

Why do skilled high jumpers lower their COM on the last step?

A) to increase time of support between foot and ground
B) to increase vertical velocity at take-off
C) to increase impulse at take-off
D) both A and B
E) all of the above

Question 40

Which type of equipment provides constant velocity?

A) isotonic
B) free weights
C) Nautilus
D) Isokinetic

Question 41

The ratio of force arm to resistance arm defines ___________________ __________________.

Question 42

The center of gravity of an object is always located within the object.

Question 43

Torque is the product of force and the perpendicular distance from the force to the axis, also known as the ___________________ ___________________.

Question 44

Explain 1 lever system within the human body, including the lever, axis, force, resistance, class, mechanical advantage and practical advantages.

Question 45

Explain the concept of net torque as it applies to a specific human movement skill.

Question 46

A motionless body is in a state of static equilibrium.

Question 47

If force is applied directly to the axis of rotation, torque will equal zero.

Question 48

Provide 2 examples in sport, dance or rehabilitation where maximum stability is desired and explain various ways this can be accomplished.

Question 49

A concept indicating a balance between applied forces and inertial forces for a body in motion is called ___________________ ___________________.

Question 50

Running barefoot results in higher joint torque at the knee than using running shoes.

Question 51

The ability to control equilibrium defines ___________________.

Question 52

When other factors remain constant, an increase in the mass of an object will subsequently increase the object's stability.

Question 53

A lever positioned with the applied resistance between the axis and the force is a ___________________ class lever.

Question 54

Explain the importance of center of gravity (total body and segmental) as it relates to human movement. Give specific examples.

Question 55

Discuss the factors that determine the force-generating capability of a muscle.