WEEK 10

Question 1

linear versus angular kinetics

Answer 1

force vs torque/moment arm

acceleration vs angular acceleration

mass vs moment of inertia

momentum vs angular momentum

impulse vs angular impulse

Question 2

define inertia

Answer 2

a bodys tendency to resist acceleration

• inertia= directly proportional to mass

the greater body mass the greater its resistance to linear acceleration

Question 3

define moment of inertia

Answer 3

the angular version of mass

during angular motion the relative ease of initiating or halting angular motion depends on the distribution of mass with respect to the axis of rotation

Question 4

what is the equation of moment of inertia

Answer 4

I = MK^2

moment of inertia = mass x radius of gyration ^2

Question 5

define the radius of gyration

Answer 5

the distance from the axis of rotation to a point where the body’s mass could be concentrated without altering its rotational characteristics

• the further the mass is distributed from the axis of rotation, the harder it is to rotate due to increased inertia

Question 6

describe the axes of rotation and moment of inertia ( traverse axes/ sagittal plane rotation)

Answer 6

• low inertia because close to the axes of rotation
• reducing radius of gyration
• low rotational inertia

Question 7

describe axes of rotation when in a “pike position”

Answer 7

• moderate/ medium inertia
• increased distance from the axes of rotation therefore increases the radius of gyration and inertia

Question 8

describe the axes of rotation when completing a layout

Answer 8

• maximum moment of inertia
• rotated around the hip joint
• further away from the point of axes increasing radius of gyration

Question 9

describe torque, inertia and angular acceleration

Answer 9

the angular acceleration of a body’s directly proportional to the net torque applied to it, and the Bodys acceleration is inversely proportional to the rotational inertia of the body

Question 10

describe constant rotational inertia

Answer 10

increase torque= increased angular acceleration

IF inertia is constant

Question 11

describe constant inertia

Answer 11

increased inertia means there is a decreased angular acceleration

IF the torque is constant

Question 12

define angular momentum and what is the equation

Answer 12

the quantity of angular motion that an object possesses

angular momentum (H= lw)

Question 13

what are the 3 factors that affect angular momentum

Answer 13

1) the body’s mass

2) angular velocity of the body

3) the distribution of the mass

Question 14

define conservation of angular momentum

Answer 14

when airborne, angular momentum is conserved as there are no forces acting upon the system

Question 15

what are the two factors to transfer angular momentum

Answer 15

1) from one anatomical body or body axis rotation to another

2) from one body part to another

Question 16

what are the two ways of generally performed transfer of angular momentum

Answer 16

1) while the system is in the air eg diving

2) while one segment end point is fixed to the ground or another surface

Question 17

describe when the system is in air

Answer 17

when the system is in air, a reaction caused by the rotation of the trunk and upper extremity in one direction, results in an equal and opposite rotation of the pelvis and lower extremities.

Question 18

define angular impulse

Answer 18

an equal to the change in angular momentum

• it is also equal to the product of torque and the time interval over which the torque acts

Question 19

define centripetal force

Answer 19

centre seeking force. my also be defined in terms of angular velocity

Question 20

define banking

Answer 20

when a surface is banked, we are no longer dependent on friction to produce the centripetal acceleration. a surface is usually banked for a specific speed