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alevel pe aqa > angular motion > Flashcards

angular motion Flashcards

1
Q

what is angular motion

A

it refers to rotation and involves turning around an axis

angular motion can be a whole body or a part of a body like arms or legs

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2
Q

examples of angular motion for a part of a body

A

throwing a discuss, arms and legs whist running, forehand in tennis

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3
Q

how do we create a turning force

A

we apply the force eccentrically

eccentric forces create more torque

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4
Q

angular motion occurs as a result of…

A

torque

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5
Q

what is torque

A

it is a turning force that causes an object to rotate around its axis

often called a moment

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6
Q

a formula that involves torque

moment of force=

A

moment of force (torque-newton meters) = force (N) x perpendicular distance from fulcrum (m)

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7
Q

if you increase the size of the force it increases torque what happens to angular motion

A

it is increased

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8
Q

how can torque be changed to have different effects on angular motion

A

if it is applied closer to or further away from the axis of movement

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9
Q

what affect does perpendicular distance from fulcrum (pivotal point) have on torque

A

the greater the distance the the more we multiply by and so the greater the torque

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10
Q

what is newtons first law in relation to AM

A

a rotating body will continue to turn about its axis of rotation with constant angular momentum unless an external rotational force (torque) is exerted upon it

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11
Q

what is newtons first law in relation to AM applied to a figure skater

A

spinning in flight they will continue to spin until they land and an external force is applied onto their skates this will change and slow their angular momentum, this force will be friction

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12
Q

what is newtons 2nd law in relation to AM

A

the rate of change of angular momentum of a body is proportional to the force (torque) causing it and the change takes place in the direction in which the force (torque) acts

the greater torque (turning force) exerted the faster the rotation

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13
Q

what does the moment of force =

(2nd)

A

moment of force (torque-newton meters)= force (newtons) X perpendicular distance from fulcrum (pivotal point) (m)

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14
Q

apply newtons 2nd law in relation to AM for lacrosse sticks

A

with a longer stick (defense) there is a longer perpendicular distance from the fulcrum so you can propel the ball with the most force

shortest stick (attack/midfield) there is a shorter perpendicular distance from the fulcrum so it allows more control

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15
Q

what is newtons 3rd law in relation to AM

A

when a force (torque) is applied by one body to another the second body will exert an equal and opposite force (torque)

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16
Q

apply newtons 3rd law in relation to AM for a tennis lpayer

A

a tennis player applies a downwards slice action on the ball it will rotate (spin) to replicate the amount of torque provided

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17
Q

what is angular displacement

A

the smallest change in angle between the starting and finishing point of rotation

the change in the angle as an object moves in a circular path

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17
Q

how many degrees is 1 radian

A

57.3 degrees

18
Q
A
18
Q

is angular displacement a scalar or vector

A

vector

19
Q

how many degrees is 1 radian

A

57.3 degrees

20
Q

how many radians/the angular displacement of 360 degrees (inc working out)

A

360 degrees is not zero displacement
360/57.3=6.28 radians

21
Q

formula for angular displacement

A

angular displacement=angular velocity x time taken

22
Q

what is angular velocity

A

rotational speed of the object, rate of change of angular displacement

23
Q

is angular velocity a scalar or vector and why

A

vector because t refers to the angular displacement that is covered in a certain time

24
Q

formular for angular velocity

A

angular velocity= angular displacement (rad)/time taken

25
Q

a performer spins from one position to another on the parallel bars, spinning 110 degrees from point x to y in 0.5 secs, what is the angular velocity

A

AD= 110/57.3 = 1.9 rads displacement

1.9/0.5 = 3.8 rad/s

26
Q

what is moment of inertia

A

the resistance of a body to angular motion (spin)
reluctance to change its current state of rotational motion

level of force that has to be applied in order to maintain inertia

27
Q

what can the moment of inertia depend on

A

the mass of the body and the distribution of mass around the axis of rotation

both can be manipulated

28
Q

how can mass affect the moment of inertia

A

the greater the mass the greater the resistance to change and therefore the greater moment of inertia

29
Q

how can the distribution of mass affect the moment of inertia

A

the closer the mass is to the axis of rotation the easier it is to rotate, this is because the moment of inertia is lower, increasing the distribution of mass away from the axis of rotation will increase the reluctance to rotate (increasing moment of inertia)

30
Q

formula for moment of inertia

A

body mass x distance from axis of rotation ^2

kg m^2

31
Q

what is angular momentum

A

the amount of angular motion of an object when turning
quantity of rotation

32
Q

what is the conservation of angular momentum

A

angular momentum is conserved when a body is in flight and there is an inversely proportional relationship between angular velocity and moment of inertia

it stays constant unless external force (torque) is applied (n1st law)

33
Q

formula for angular momentum

A

moment of inertia x angular velocity

kg m^2 / sec

34
Q

what is angular acceleration

A

the rate of change of angular velocity

35
Q

formula for angular acceleration

A

change in AV (rad/s)/time taken

rad/s^2

36
Q

to increase angular velocity what do you do

A

increase the moment of inertia
distributing the mass further away from the centre of gravity

spread out the body

37
Q

to decrease angular velocity what do you do

A

decrease moment of inertia
distributing the mass closer to the centre of gravity

tuck the body in

38
Q

apply the moment of inertia to a sprinter

A

driving leg (extending) is far from the hip and therefore has a large moment of inertia

the recovery leg that flexes allows its mass to travel closer to the axis of rotation and therefore moves quicker as it reduces to the moment of inertia

39
Q

gymnasts have to change the position of their body when performing a somersault during a floor routine

explain how a gymnast alters their angular velocity by changing their moment of inertia (4)

A

angular momentum= moment of inertia x angular velocity (during rotation)
angular momentum remains constant/conservation of angular
momentum.

to slow down (rotation) gymnast increases moment of inertia.

achieved by extending body/opening out/or equivalent

to increase speed of rotation gymnast decreases moment of inertia

achieved by tucking/bringing arms towards rotational axis

40
Q

explain how a gymnast can alter the speed of rotation during flight (8 marks)

A

changing shape of the body will causes a change in speed.
change in moi leads to change in av/speed of rotation.
angular mom remains constant
angular mom=moi x av
av is speed of rotation
moi- distribution of mass around axis/reluctance of the body to move.
to slow down rotation increase moi done by extending out body.
to increase speed decreases moi achieved by tucking the body in.

draw diagram

41
Q
A

alevel pe aqa (35 decks)

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