Exam 2: Mechanical Principles: Kinetics

Using crutches ______________ an individual's base of support.

When a body part is positioned and supported to move in a plane perpendicular to the earth, the effects of gravity are reduced so a muscle weaker than 3/5 is able to move a segment.

Third class levers, although mechanically inefficient, offer the benefit of a large excursion in range of motion with little or small changes in muscle length.

Your patient is having difficulty performing shoulder abduction from 0 to 90 $\degree$ with a cuff weight around his forearm while sitting in a chair. To make the exercise as easy as possible you recommend that he or she move the cuff weight ____________ and perform the activity in a _________ position.

Assuming a right triangle, to calculate the cosine of theta one should:

The center of gravity rises when an individual elevates his or her arms overhead.

Vector forces can be combined when more than one force is applied to a body or segment.

According to Newton's Second Law of Motion:

Whenever the force arm of the muscle working is shorter than the resistance arm of the segment moved by the muscle, the muscle must exert less force to lift the segment.

A torque's greatest magnitude occurs when the direction of application is at a right angle or 90 $\degree$ to the segment or extremity.

The "normal" force vector is primarily responsible for producing:

If insufficient, this source of force may promote instability:

A body is stable when the line of gravity runs __________the center of its base of support.

Small forces imparted to the distal aspect of an extremity (i.e., ankle) create large torques to the proximal joints (i.e., hip).

Your patient is performing shoulder flexion from 0 to 180 $\degree$ in a standing position with his elbow extended while holding a 5-pound weight in his hand. The torque imposed by the 5-pound weight is greatest at ______ $\degree$ .

Which of the following represents the least degree of stability?

Archimedes' principle states that a body submerged in a liquid is buoyed up by a force ___________ the weight of the liquid displaced.

When the body or a body segment moves over a surface, friction also is a torque that affects movement.

To reduce the effect of weight on a joint a clinician could:

Theoretically as it relates to lever arms, sit-ups are most difficult when the arms are positioned __________ of the individual.