Seesaws

Question 0

2 Physical Quantities of Rotational Motion?

Answer 0

1) Angular Position (Rotation)
2) Angular Velocity

Vector quantities

Question 1

Newtons First Law Rotational Motion

Answer 1

A rigid object that’s not wobbling & free of external torques, rotates at constant angular velocity.

Question 2

i) Rotation to your right

ii) Rotation to your left

Answer 2

i) Downward rotation

ii) Upward rotation

Question 3

3 ways measure Angular Position

Answer 3

1) As a degree ex. 90*
2) Rotationally ex. quarter, half turn
3) Radius ex. Pi/ 2 radius down

Question 4

Angular Velocity def & tells (3)?

Answer 4

Rate objects angular position change w/ time

Tells:

1) speed object going through angles
2) axis object’s spinning
3) (right hand rule) specific direction about axis

Question 5

Torque

Answer 5

Twisting force causing rotation.

-changes pivoting objects angular velocity & violates N’s 1st Law of Rotational Motion (has external torque/influence & .•. not rotate constant angular velocity)

Question 6

Seesaws Rotational Inertia affected every time_____?

Answer 6

Seesaws ends hit ground (exerting external torque)

Question 9

Angular Acceleration

Answer 9

Rate at which angular velocity change w/ time

- vector quantity of rotational motion

Question 10

Net Torque

Answer 10

1/more total torques acting upon object

- causes angular acceleration

Question 11

Angular Acceleration causes (2)?

Answer 11

1. Net Torque

2. Rotational Inertia (mass): resistance to angular acceleration

Question 12

A larger net torque has a ____ acceleration & a smaller net torque has a _____ acceleration

Answer 12

1. Larger

2. Smaller

Question 13

Angular Acceleration proportional (keeps constant ratio)?

Answer 13

Net Torque acting upon object

Question 14

Angular Acceleration inversely proportional?

Answer 14

Seesaws rotational mass

Question 15

Newton’s 2nd Law of Rotational Motion

Answer 15

Angular Acceleration = net torque/ rotational mass

Question 16

Torques produce x & x produces Torques

Answer 16

Forces

Question 17

Can’t produce torque in what direction from objects centre of rotation?

Answer 17

Toward/away from/ on objects’ centre of rotation

Question 18

Can produce torque in what direction from objects center of rotation?

Answer 18

Exerting force perpendicular to lever arms vector (amount & direction: determine 1 point in space relative another) direction.

Question 19

Objects vector extends from?

Answer 19

Objects centre of rotation to point where force exerted (extension b/w points is vector)

Question 20

Torque =?

Answer 20

Lever arm • force (only force perpendicular to lever arm incl.)

Question 21

Torque you exert on bolt (w/wrench) about its centre of rotation=?

Answer 21

Your force• (wrenches) lever arm extension

Question 22

Lever

Answer 22

A rigid bar resting on a pivot.

Question 23

Forces are at ____ to lever arms

Answer 23

Right angles

Question 24

Torques are located?

Answer 24

90• horizontal to the downward force & perpendicular to the lever arm.

Question 25

2 ways seesaw balanced?

Answer 25

1) sum of torques = 0 (cancel out)

2) riders & seesaw together have Center of Gravity vertically above pivot & .•. produce no torque.

Question 26

The two torques produced by the objects on the seesaw are____ each other.

Answer 26

Opposite.

Question 27

Moving object (& force) position lower down lever arm (closer to pivot) increases/decreases torque it produces.

Answer 27

A shorter lever arm decreases the torque it produces & is closer to the COR.

Question 28

To produce 0 torques (balance) objects w/ same weight, must be equidistant from ____ & .•. have same _______.

Answer 28

The center of rotation & .•. have same lever arm distances from pivot.

Question 29

The lever arms are in the same direction so the objects____ are in the same direction.

Answer 29

Torques

Question 30

Center of Gravity

Answer 30

The effective location of an objects weight (downward acceleration) - all about forces (gravity) - point over which object can be perfectly balanced; net torque due to gravity about that point = zero

Question 31

Center of Mass

Answer 31

Effective location objects mass, it's natural pivot - all about inertia & motion - the average location of the mass distribution - objects Center of rotation: Point about which all physical quantities of rotational motion are defined. - point that stays put as object spins (the pivot)

Question 32

For (small) objects.....

Answer 32

G

Question 33

COG proportional ____

Answer 33

Centre of mass

Question 35

Riders @ ends of board higher/lower rotational mass?

Answer 35

Higher & .•. riders closer to pivot have lower rotational mass.

Question 36

Every piece of____ contributes to an objects rotational mass & depends on (2)?

Answer 36

Mass: 1) where portion ordinary mass is 2) how far portion ordinary mass from pivot (axis of rotation)

Question 37

Rotational mass contributed by ordinary mass=?

Answer 37

Ordinary mass • distance b/w ordinary mass & axis of rotation

Question 38

Rotational Mass depends on____?

Answer 38

The location of your axis of rotation

Question 39

Tennis Racket has 3 rotational masses (ordered by rotation)

Answer 39

Smallest: rotation about the vertical axis (most of mass close to axis) Larger: rotation about the horizontal axis. Largest: when COR located at either end of racket & pivot about such point.

Question 40

Two objects dropped simultaneously w/ same force & at same distance from ground but different masses, which falls first?

Answer 40

Object w/ more angular acceleration & .•. more angular velocity. Object w/ < mass.

Question 41

You fall of a cliff, what's the cause (i) & resistance (ii) angular acceleration of your body?

Answer 41

(i) C: Net Torque on you (due to gravity) | (ii) R: Your rotational mass

Question 42

Rotational Mass=?

Answer 42

Mass• distance^2

Question 43

You & child 1/2 your height fall @ same angle, same distance swimming pool Who hits water 1st?

Answer 43

The child has more angular acceleration & more angular velocity. - You have 2x weight • 2x lever arm (2x as far your COG from axis of rotation- feet) = 4x Net torque - You have 2x mass • 2x distance (on average) from AxofRot RotMass= mass• distance^2 .•. 2x mass • 2x distance^2 = 8x rotational mass of child. Have 4x net torque but 8x rotational mass. Angular Acceleration = Net torque/mass 4/8= 1/2 Angular Acceleration vs child.

Question 48

Unsupported object thrown straight up in air doing 2 types motion?

Answer 48

1) Translational- it's center of mass falling in arc of falling objects 2) Rotational- rotating about its center of mass (it's natural pivot)

Question 49

Find objects center of mass method?

Answer 49

Place object on flat surface & spin it: object naturally spins about its center of mass (point stays put as object spins)

Question 75

The farther riders mass from the pivot | the greater seesaw's _____ _______ ____ & the slower it's _____ _______.

Answer 75

1) overall rotational mass | 2) angular acceleration

Question 86

How do seesaw riders riders affect each other?

Answer 86

They support each other (cancel weights- keep from falling) & exchange energy (through seesaw & torques) as seesaw rotates back & forth - 1 exerts torque on 2 about the pivot - 2 exerts torque on 1 about the pivot

Question 87

N's 3rd Law of Rotation

Answer 87

For every torque object (i) exerts on (ii), object (ii) exerts an equal but oppositely directed torque on object (i).

Question 88

Torque Units

Answer 88

S.I: Nmeter (m away from pivot) Eng: FootPound (1 pound/foot away from pivot)

Question 89

When lowering (unbalancing) seesaw lowered & raised object transfer energy, what occurs w/ distance

Answer 89

Work= force•distance - Lowered object has > (downward) force but < distance - Raised object has < (upward) force but > distance - Both work cancel each other out & obey N's 3rd law rotation

Question 90

To increase work on screwed nail with hammer (plucker)...

Answer 90

Increase the lever arm distance from pivot. Work You're doing on hammer: Small force & large distance. Work hammer doing on nail: Large force & small distance

Question 94

When the gravitational field across an object is uniform _____ & ______are identical.

Answer 94

COG & COM