quizzes for test 2
What is the torque if a 50 N force is applied 2m from the axis of rotation
100Nm
what is the average angular velocity of an object moving through 30 deg in 2 s?
15 deg per sec 30/2
The moment arm of the biceps brachii muscle about the elbow joint is largest when the angle at the elbow joint is approximately
180
calculate the moment of inertia when an object's mass is 12kg and the mass is distributed 4m from the axis of rotation
192 kg*m2 i=mk2 (12)(4)2 192
What is the net torque when you are holding a 10 lb weight 1 ft from your elbow (producing a clockwise torque) and your biceps is generating a 50 lb force with a moment arm of 3 in. (producing a counterclockwise torque)?
2.5 ft lb
a discus thrower exerts a torque of 5Nm on a 2kg discus. the discus has a radius of gyration of 10cm. if this is the only torque exerted on the discus, what is its angular acceleration?
250 rad/s^2 t=ia 5Nm=2(.10)^2 5/0.02 250
in the human body, most o the lever systems formed by muscles pulling on bones are what class?
3rd class
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 2.0 m, what is the linear velocity of the club head?
40m/s 2*20
During a trampoline routine, a gymnast is 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?
5 rad/s
A person performs a bench press. The bar's mass is 50 kg. When this person's arms are extended, the bar is 0.6 m above the starting point. How much work did the person do to push the bar off his chest to full extension of his arms?
50 kg * 10 fg = 500 * 0.6m = 300m
For any given muscle, the moment arm is largest when the angle of muscle pull on the bone is closest to
90
which of the following motions occurs primarily in the frontal plane
a cartwheel
An angle formed between two body segments is an example of
a relative angle
torque is defined as
all of the above the tendency of a force to cause rotation. the turning effect of a force, the product of a force and moment arm, and angular.
the center of gravity of a box of uniform density is located
at the exact center of the box
a gymnast dismounts the uneven parallel bars with some angular momentum about her tranvserse axis. just after release, she is in a piked position. she then extends into a layout position before she lands what happens as a result of this action?
her moment of inertia increases and she rotates slower i bigger= rotate slower i smaller= rotate faster
stability may be increased by
increasing the size of the base of support
Mechanical work is performed in all of these types of muscle activity (contraction) except for
isometric
as an object's mass increases, what happens to its moment of inertia
it increases
When knee flexion is increased, what happens to the moment of inertia of the leg about the hip?
it is decreased
If a force acts directly through an object's center of gravity, _______ acceleration will occur.
linear
A force not directed through the center of an object (an eccentric force) tends to cause
linear and angular acceleration
The force to be considered in calculating the work you perform when climbing up a set of stairs is your
mass
For most segments of the human body, the segmental center of gravity is located
more proximally
calculate the magnitude of the angular momentum if an object's moment of inertia is 50kg*m2 and its velocity is 10m/s
need more info?
a centric force
passes through an axis of rotation
in the equation for moment of inertia, which variable is most influential?
radius of gyration
The form of energy associated with the stiffness and deformability of an object is called
strain energy
In the equation for calculating strain energy, the x symbolizes
the amount of deformation
For a rotating object, the acceleration directed toward the center of rotation is called
the centripetal acceleration
what is the relationship between torque and angular acceleration?
the greater the torque acting at the axis of rotation, the greater the angular acceleration of given body
During angular motion, what is the relationship between the length of the moment arm and the torque created (when the force used is constant)?
the longer the moment arm, the greater the torque
A moment arm is best described as
the perpendicular distance from the line of action of a force to a specified axis of rotation
As a football player moves from a two-point stance (standing) to a four-point stance (hands and feet on the ground),
the player's stability is increased
angular impluse is the product of
torque and the time toque is applied
which plane is perpendicular to the longitudinal or vertical axis?
transverse
In the kinetic energy equation, which component is most important?
velocity
which is not a unit of angular displacement?
watt
