Grade 12 physics

Rotational motion def?

motion of an body that spins about an axis

a point on an object that rotates about a single axis undergoes?

circular motion

that circular motion changes its what constanly?

its direction

delta theata is equal to ?

s/m in which both are in meters and its unit is rad

how do we change from rad to degree to revolution

red to dgree we times by 180/pi and degree to revolution rev divide by 360 and rad to rev we multiply by 1/2pi

radian is an angle whose? Which its aproximatly equal to?

arc length is equal to its radius , 57.3 degree or 1/2pi rev

when we have 1 revolution the arc length is equal to?

2 pi r

to gte arc length from degrees or rad what do we do? Or another way?

we turn it into rev and our arc length is equal to n(2pir), when we have radius and radian we do s= theata x r

angular displacement def?

the angle through which a point or line or body is rotated in a specified direction and about a specified axis

angular displacement is equal to?

Deltta s over r

our angular dfisplacement must be in what unit?

must be in rads

when is it positeve and when is it negative?

clockwise is negative anti clockwise is positeve

in angular displacement what is constant?

the radius is constant

angular speed

the rate at which a body rotates about an axis, or time rate of change of angular displacement usually expressed in radians per a second

angular speed is equal to?

omega= delta angular displacement/ delta time

the unit of angular speed in equations should be? So how do we change them into that?

rad/sec if rev/s we do x2pi if its degree/s we do pi/180

If its rev/min we do 2pi/60

the constanat angular speeds are ?

1rev/60s

1rev/3600

1rev/86400

1rev/year(24×3600×365.25)

1rev/24×3600

for an object to remain rigid every portion of the object must have the same?

angular speed if not the shape of the object will change

diffrence between linear speed and angular speed?

linear speed is the distance at which a body traverls during a time interval

Angular speed; the angular displacement during a time interval

all of the omega constants are? Why are they negative? So when we have extyarats and one is negtaive and one is posisteve which one would we chose?

negative cuz they rotate clockwise , we chose the negative one

Angular accelerations def?

the time rate of change of angular speed expressed in radians per second per second

angular aceleration is equal to?

omega/ delta t which is equal to rad/s²

what should i focus on?

if there is no change is omega then angular acceleration is zero

for an object to remain rigid? if not?

all of its points must have the same angular acceleration . The shape of the object will change

When do we use rotational and linear kinematic equations? When its constant what do we use?

when the motion is not constant, we just used the normal omega and yasas

when an object deacelerates does omega become negative? then what becomes negative?

nope only direction wise becomes negative, alpha and aceleration

when ever an object rolls once what can be equal to what? NOT THEATA

delta x and delta s can be equal to one another

when omega= angular dispalcement/delta t cant be used?

when there is a change in motion

Relation between angular speed and tangential acceleration is?

direct

Section 2

tangetntial speed def?

the instanteous linear speed of an object directed to along the tangent to the objects circular path

the tangent to a circle is a line that touches the circlae at … point

one

tangential speed is the instantaneous …. ….. of an object d

linear speed

that is directed along the …. To the objects …….

tangent circular path

when an object rotates everyt point has the same angular speed but diffrent vt why is ithat?

cuz of diffrence in radius

what is the formula for vt?

vt=wr

how do we get that formula?

delta theta= delta s/r

what is the unit of vt?

m/s

which value is constant in this equation?

its omega

what about the angular displacement? Speed? Acceleration?

R, t ,t

what on all points of the body are the same?

omega is

velocity is a vector quantity so it can change either by?

magnitude or direction

tangential aceleration def?

The instaneous linear ….. of an object directed to the … of the objects …. Path or its the time rate of change of …… ….. in the tangential direction of the circular motion

acceleration. Tangent, circular, instataneous speed

vt and at are first equal to what?

vt is equal to delta x/ delta t

At is equal to delta vt/delta t

From which formula do we get at formula from and what is at formula?

From vt=wr

what are the three things that must be the same for all points otherwisse the object deforms?

all three angulars

centripetal acceleration

The time rate of the …. Of the …… of ….. when it moves on a …. ….

variaition, direction , velocity, circular path

centripetal aceleration?

Its the time rate of variaition of the direction of velocity

The aceleration of an objecrt when it moves on a circular path

Its direction to the center of circular path

Its perpendicular to tangential speed

what are the formulas of ac?

ac= vt squared/ r

Ac= wsquare r

Ac= vt w

at constant speed r is ….. propertional to ac

At constant angiular speed r is ….. propertional

inversly, directly

when ever we have a graph and ac is pernpendicular to vt then we have a ….. graph

circular

every object on a circular path has a centripetal acceleration because it?

changes its direction continuasly

unifom circular motion ocures when?

acceleration of constant magnitude is perpendicular to the tangential velocity

At def and ac?

its the the time rate of change of magnitude of velocity

Its the time rate of changing the direction of velocity

to ddetermine the total acceleratoon we can use the? to find the direction we can use the? we can also use?

pythagoreon thereom , tantheata= ac/at which becomes theta = yk

We can also tan omega squared/alpha cuz we can change their formulas

A racing car rounds the turn at a constant velocity of 145km/h is this corfrect?

nope isnt constant veclcotuy cuz direction changes

describe the path of. Amoving body whose acceleration is consnat it manitude at all atimes and is perpendicular to the cirrcle

its circular poath

velocirty has magnitude and direction and so does?

Acceleration

give an example in which an automobile crriver can have a centripetal acceleration ghyt no tangential acceleration?

driving the car in circulare path at constant speed

can a car move around a circular race tracjk so that the car has a tangential acceleration buyt no centripetakl aceelleartion?

nope ac is necesary for circular path

The gas pedal and the brakes of a car accelerate and deaclerate the car could a streering wheel perform eitehr of these two actions?

yep change the direction causes a change in velocity

diffrence between ac and alpha?

ac is the time rate of changing the direction of vt and directed to teh centefr of the circular path

Tiem rate of changing of angular speed

when is ac=0? Even in the example he got and we all got it wrong?

when we dont have a circular path , when it was a rotating object but didnt specify a point on that specific object

any object moving in a circular path MUST have?

ac.

Vt and at … exist without a circular otha

CAN

the angle between vt and ac is?

9

the angle between at and vt?

0

only which quantities haev rads in them?

Only angular

at constant speed is vt the one being zero?

Nope at is

accelerate and aceelartion is used asa general term fro?

Slowing down going faster and cahnging direction

fc def?

the resultant effective force on a body that moves it in a circular path and its directed towards the center of that circular path

any object moving ain a circular path must have a … …. Exerted on it and that is directed towards the …. Of that circular path

net force, center

the reason for circular motion is

centripetal force

according to newtons second law?

fc=mac

Fc=m vsquared/r

Fc=mromega squared

at constant speed what is the relation between fc and r

At constant angular speed?

inverse

Direct

centripital force is directed towards the center of the circular path and its perneopdnciular on the direction?

motion vt t

the angles between c and c? T and c? But vt and at when slowing down?

0 90, 180 degree

centripetal force has many forms for example?

friction between a race cars tires and circular racetrack its the force that enables the car to travel in a circular path

Gravitational force is the force that kleeps moon in its orbit around earth

what happens if fc vanished? it causes a change in the direction of?instead of circular path it moves along? because of what?

because fc is at a right angle to the motion it causes a change in the direction of velocity , a straight line path tangent top the circle , because of inertia

When the ball breaks of at position of right at which direction will it go? What about if it broke off at the top of the path?

vertically upward and it freefall, parabolic path

as a driver makes a sharp turn the passenger moves right

an object has a tendency to move in a straight line and that is acoording to tnewton first law of inertia which states the natural tendency of a body is to continue moving in a straight line

thereis no force called ….. the reason moving bodies in straight line when centripetal force vanished is?

centrifugal inertia

normal forca is always? And we have it when?

Perpendicular to the surface, an object is in contact with a rigid surface

what maintains the circular motion of the following

A bicyclist moving around a flat circular track

A bicycle moving around a flat circular track

A bobsled turning a corner on its track?

fn of man on seat friction between bicyclist and seat and the fn of byciklyst grasping the seat so 3 forces

friction force between tires and track

Normal; force from the curve parts of the track

if u attack an object to a spring and spin it arouynd does the spring stretch? Why? What force maintains circular motion?

yes it moves in a spiral path and that is because of inertia the object distance increase outward until the spring force f=-kx is great enough tio keep the obvject at a constant radius

Fe elastic is the one that is equal to fc

why does the water remain in a pail tyhat is whirled in a vertical path?

the water tend sto move in a straight line due to inertia

And the water an dpail have the same acceleration.

What if spring was replaced by string?

thjen no the obk woll just move in a circular ptah and fc will be equal to ft

when does our object deforms and our object becomes bigger?

when inertia is greater than fc

why is earth not spherical in shape? And bulges at the equator?

Because eth eforce with particles of earth is not enough to resists the inertia of the points located at the equator

or because?

high temp causes the core of earth materials to become liquid state and centripetal force derceases at th equator

because of earth rotation youy woukld weigh slighl;y less at the equator that you would at the poles explain?

on the equator there is a part of gravitartional force that jkeeps you in circular motion making gravitational force of earth less weight

what value is the same at poles and at equator?

mass is

at the poles we have no fc but what is the relation between fg and fn?

they are both equal

why does mud fly of a rapid turning wheel?

cuz of inertia cohesion is not able to provide enough force

Muds inertia exceeds the cohesion force

When we have a string and we spin it what is the value of ft at the buttom of the circular path?

its the greatest cuz fe = fg + fc

are bodies in a ciruclar path in equalibirum?

Nope because of the unbalanced force acting on it

force neede d to maintain the circular motion is ..

Any force directed to the … of the circular ptha is ..

If the object remains in circular ptah under gravity or gravity holds te object in circular path it means that?

fc

Center, fc

Fc=fg

When only gravity is the one keeping the object in a circular path the velocity can be equal to?

And we can also say ac=?

v=square root of rg

G

If u see a questin where car moves around a flat circular path the force which keeps the car in circular ptha is?

the friction

to determine the coeficient of static friction between the tires and the road or the sped of car without skidding we use which method? the three dif formulas?

fc=fs fn=fg

Vsquared/rg

Ac/g

Wsquaredr/g