Biomechanics 13

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

1667 N

In the human body, most of the lever systems formed by muscles pulling on bones are what class? A. 1st class B. 2nd class C. 3rd class D. no particular class is dominant

3rd class

The resistance arm (RA) will always be longer than the force arm (FA) in what class lever? A. 1st class B. 2nd class C. 3rd class D. none of the above

3rd class

A claw-tooth hammer being used to pry up a nail is an example of which class of lever? A. 1st class B. 2nd class C. 3rd class D. not a lever

1st class lever

A seesaw is an example of which class of lever? A. 1st class B. 2nd class C. 3rd class D. not a lever

1st class lever

A wheelbarrow is an example of which class of lever? A. 1st class B. 2nd class C. 3rd class D. not a lever

2nd class lever

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

A and B A. created by equal forces on opposite sides of an axis B.created by forces acting in the same angular direction

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

A. the stabilizing component of muscle force

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

A. the center of mass

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

A.resistance varies over the range of motion with Nautilus equipment

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

B. a Sumo wrestler's crouched defensive stance

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

B. segmental COM is the point of resistance (where weight vector is drawn) and therefore determines the length of the resistance arm

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

Both A and B

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

Both A and B A. applies to bodies in motion B. first identified by D'Alembert

Which of the following will improve leverage? A. increase force arm B. decrease resistance arm C. both A & B D. none of the above

Both A and B A. increase force arm B. decrease resistance arm

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

C. both A and B A. the amounts of tension generated by the muscles B. the arrangement of the muscles around the joint

Which type of equipment provides constant velocity? A. isotonic B.free weight C. Nautilus D. Isokinetic

D. Isokinetic

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

D. all of the above

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

D. move COM to edge of BOS

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

E. all of the above are correct

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

all of the above

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

all of the above

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

all of the above

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

all of the above

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

all of the above

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

all of the above

The ability to control equilibrium defines what? A. stability B. balance C. mobility D. center of mass

balance

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

both A and B

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

both A and B

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

both A and B A. control velocity of movement B. enhance stability of the joint

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

both A and B A. momentum B. kinetic energy

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

concentric

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

decrease mass

Torque is the angular analogue of what? A. momentum B. force C. mass D. impulse

force

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

it will move up

The perpendicular distance between the line of force and the axis defines what? A. torque B. fulcrum C. moment arm O D. none of the above

momentum arm

Which of the following will benefit mobility? A. increase mass B. increase base of support C. increase friction D. raise center of gravity

raise center of gravity

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

the lee-saw will tilt to the left

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

the mechanical advantage of the lever

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

the rotary component of muscle force