angular motion

Question 1

define angular motion

Answer 1

movement of a body or part in a circular path about an axis of rotation (radians)

Question 2

what is the val of one radian

Answer 2

57.3 degrees

Question 3

how is angular motion created

Answer 3

eccentric external force applied outside the centre of mass

Question 4

describe longitudinal axis

Answer 4

runs head to toe e.g. pirouette

Question 5

describe transverse axis

Answer 5

runs left to right e.g. somersault

Question 6

describe frontal axis

Answer 6

splits you front and back e.g. cartwheel

Question 7

give a sporting example for each axis of rotation

Answer 7

• longitudinal: pivot in netball, pirouette
• frontal: cartwheel
• transverse: somersault

Question 8

define moment of inertia

Answer 8

distribution of mass from the axis of rotation measured in kgm^2

Question 9

formulae for calculating moment of inertia

Answer 9

moment of inertia = angular momentum/ angular velocity

OR

sum of (mass x districution of mass from axis of rotation squared)

Question 10

define anglar velocity

Answer 10

the rotational speed of an object and the axis the object rotates around

Question 11

formulae for calculating angular velocity

Answer 11

angular velocity = angular displacement( rad)/ time(s)

Question 12

define angular momentum

Answer 12

the quantity of angular motion possessed by a body (kgm^2rads^-1)

Question 13

formulae for angular momentum

Answer 13

angular momentum = moment of inertia x angular velocity

Question 14

explain the factors affecting the size of moment of inertia of a rotating body

Answer 14

• mass of the body: greater the mass, greater the resistance to change and therefore greater moment of inertia
• distribution of mass round axis of rotation: decreasing distance from axis increases angular velocity as moment of inertia is low, increasing distribution of mass from axis decreases angular velocity as moment of inertia is high

Question 15

describe the relationship between moment of inertia and angular velocity

Answer 15

inversely proportional to each other, when one increases, the other decreases.

Question 16

explain the conservation of angular momentum due to newtons laws of motion

(angular analogue of newtons 1st law)

Answer 16

• angular momentum is. conserved quantity so stays constant unless external force acts upon it (Nwewton’s 1st law)
• a rotating body will continue in a state of constant angular momentum until acted upon by an external torque.

Question 17

what is angular analogue of Newtons 1st law of motion

Answer 17

a body will continue to rotate about its axis of rotation with constant angular momentum unless acted on by an eccentric force

Question 18

explain why moment of inertia is low

Answer 18

because the distribution of mass is close to the axis of rotation e.g. arms and legs are tucked in close to the axis of rotation

Question 19

explain why moment of inertia is high

Answer 19

the distribution of mass is away from the axis of rotation e.g. arms and legs are away from tge axis of rotation