Exam 2.1 TB Flashcards
The moment arm is defined as:
The perpendicular distance from the line of action of a force to a specified axis of rotation
Torque is defined as
a. the tendency of a force to cause rotation
b. the turning effect of a force
c. the product of force and moment arm
d. all of the above
e. none of the above.
All of the above
The moment arm of the biceps brachii muscle about the elbow joint is largest when the angle at the elbow joint is approximately
90°
If I pushed a book across the table but the force was eccentric (not through the center of the book) I would create
Both linear and angular acceleration
What is the torque if a 50N force is applied 2m from the axis of rotation?
100Nm
An eccentric force
a. causes flexion
b. causes extension
c. passes through an axis of rotation
d. does not pass through an axis of rotation
e. none of the above
d. does not pass through an axis of rotation
As a joint is moved through its range of motion when strength training with free weights, such as doing the arm curl, the moment arm for the muscle crossing the joint will get
a. longer
b. shorter
c. either a or b
d. none of the above
c. either a or b
If the moment arm is 5cm and the force is 100N, the magnitude of the torque will be
5N
To determine the length of a moment arm, you would measure
a. the perpendicular distance from the axis of rotation to the force’s line of action
OR
b. the perpendicular distance from the axis of rotation to the force’s point of application
a. the perpendicular distance from the axis of rotation to the force’s line of action
In the average female, the center of gravity is located
Lower than in the average male
Which of the following motions occurs primarily in the transverse (horizontal) plane?
A pirouette.
As a football player moves from a two-point stance (standing) to a four-point stand (hands and feet on the ground)
The player’s stability has increased.
When a human body is airborne (e.g. when a person leaps through the air)
a. the body’s center of gravity follows a parabolic flight path
b. movement of the arms and legs will not influence the flight path of the center of gravity
c. air resistance influences the flight path of the center of gravity, but not significantly
d. all of the above
e. none of the above
d. all of the above
For most segments of the human body, the segmental center of gravity is located
More proximally.
Which of the following motions occurs primarily in the frontal plane?
a. running
b. cartwheel
c. a pirouette
d. all of the above
e. none of the above
b. cartwheel
The principle or law used to describe a lift is called
Bernoulli’s principle
The vertical force that always acts upward is
Buoyant force
Which shape is most conducive to optimizing lift?
a. sphere
b. foil
c. oblong
d. rectangle
e. square
b. foil
Which of the following motions occurs primarily in the sagittal plane?
a. running
b. a cartwheel
c. a pirouette
d. all of the above
e. none of the above
a. running
For a submerged object, the buoyant force acts at the
the center of volume
The concept that explains how a spinning baseball changes direction is called
The Magnus Effect
As relative velocity increases, the fluid force acting on an object increases linearly.
T or F
False
For a body to be in static equilibrium
a. all forces acting on the body must sum to zero
b. all torques acting on the body must sum to zero
c. the body must be stationary
d. all of the above
e. none of above
d. all of the above
Two forces acting on an object to cause only rotation of the object create
a force couple
When cycling forward in a straight line, the knee is rotating about a(n) _______ axis.
Transverse
A person riding a bicycle in a straight line would be moving in the
Sagittal plane
Calculate the moment of inertia when an object’s mass is 12 kg and the mass is distributed 4m from the axis of rotation
192 kg x m2
Calculate the magnitude of the angular momentum if an object’s moment of inertia is 50 kg x m2 and its velocity is 10 m/s
Need more information to calculate.
During a trampoline routine, a gymnast tumbling in the air at 20 rad/s in a tuck position. He then extends into a layout position and doubles his radius of gyration just before landing on the trampoline bed. How fast is his angular velocity at this instant, just before landing on the trampoline bed?
NOT SURE, FIGURE OUT LATER (5rad/s?)
A gymnast dismounts the uneven parallel bars with some angular momentum about her transverse axis. Just after release, she is in a piked position. She then extends into a layout position just before she lands. What happens as a result of this action?
Her moment of inertia increases and she rotates slowers.
When knee flexion is increased (heel brought to buttocks) during running, the moment of inertia of the lower extremity about the hit
Is decreased.
The center-directed acceleration of a spinning object is called
Centripetal acceleration
Angular impulse is the product of
torque and the time that torque is applied
As an object’s mass increases, what happens to its moment of interia?
This depends on how the added mass is distributed.
In the equation for moment of interia, which variable is most influential?
Radius of gyration.
What is the relationship between toque and angular acceleration?
The greater the torque acting at the axis of rotation,
The greater the angular acceleration of a given body.
When a body is completely motionless, it is considered to be
In static equilibrium
The statement “a rotating body will remain in a state of constant angular motion inless acted on by an external torque” refers to
Newton’s first law.
Which quantity causes a change in angular momentum?
a. Linear Impulse
b. Impact
c. Torque
d. Linear Acceleration
e. Angular Impulse
Angular impulse.
A diver attemps a 1 1/2 front flip in a tuck position off the 1m board, but only rotates 1 1/4 times. Which of the following suggestions is NOT appropiate for the diver?
a. Jump Higher
b. Tuck looser
c. Tuck sooner
d. Release tuck later
e. Generate more angular momentum going into the dive
b. Tuck looser
Sasha Cohen does a triple tow loop and rotates three times around 1 second. What is her average angular speed during this jump?
3 rev/s
Movement of the hand at the wrist toward the ulnar side of arm is
Ulnar deviation
Which plane is perpendicular to the longitudinal axis?
Transverse
Which of the following is not a unit of angular displacement?
a. radian
b. revolution
c. degree
d. watt
e. all of the above are units of angular displacement
d. watt
An angle formed between two body segments is an example of
A relative angle
An angle formed between a body segment and a horizontal reference line is an example of
An absolute angle
What is the average angular velocity of an object moving through 30° in 2 seconds?
15° per second
During a golf drive, the angular velocity of the driver is 20 rad/s just before impact with the golf ball. If the distance from the club head to the axis of rotation is 2.0m, what is the linear velocity of the club head?
40 m/s
The angular distance covered by a rotating object will always be
At least equal to, if not greater than, the angular displacement covered by the object
Pronation of the ankle (subtalar joint) combines the motions of
eversion, abduction, and dorsiflexion
The center of gravity of a ring of uniform density is located
NOT SURE IF THIS IS CORRECT
Outside of the object
Q11
Which form of drag would have the greatest effect on a swimmer performing the crawl (freestyle) stroke in a smooth ocean?
NOT SURE IF THIS IS CORRECT
Form Drag
Q19
