physics - La Quinta High School

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31 Οκτ 2013 (πριν από 3 χρόνια και 9 μήνες)

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PHYSICS

Final Exam Review (Day 1)

FINAL EXAM REVIEW: DAY 1 OVERVIEW


Energy Lecture Review


Kinetic & Potential Energy


Net Work (
W
net

=
F
net

D
x


F
net

cos

q
)


Work
-
Kinetic Energy Theorem (
W =
D




Conservation of Energy (
KE
i

+
PE
i

=
KE
f

+
PE
f
)



Problem Review (Group Problems)


Energy


Net Forces

ENERGY


Potential Energy


Stored Energy
In Which An Object May Use To
Perform Work On Another Object


Gravitational Potential (
PE =
mgh
)


Elastic Potential (
PE = ½ kx
2
)


Chemical Potential (
PE =
nC
v
D
q
)


Kinetic Energy


Energy Achieved By An Object
In Motion


Kinetic Energy (
KE = ½ mv
2
)

NET WORK


Work Done On An Object With Multiple Forces
Is The
Net Work


For A Net Force Applied At An Angle
, The
Net
Work

Is The Product Of The
Component Of
Force In The Direction Of Motion
& Its
Displacement



W
net

= F
net

D
x = F
net

cos
q

WORK
-
KE THEOREM


Work Done
On

(Net External Force) An Object
Results

In A Change In The Object’s
Kinetic
Energy


Work = Force x Displacement or
W = F
D
x


Work
-
KE Theorem Is Equivelent To The Following
Expression:


W = KE
f



KE
i

= ½ mv
f
2



½ mv
i
2

CONSERVATION OF
ENERGY


Total Mechanical Energy (
ME = KE + PE
) Of An
Object Remains Constant As The Object Moves


Assume
No Net Work Done
By
External Forces
(e.g.
Friction, Air Resistance, Pressure, etc.)



ME
i

= ME
f



KE
i

+ PE
i

= KE
f

+ PE
f



PROBLEM #1: WORK

The Drawing Shows A
Boat Being Pulled By
Two Locomotives
Through A Canal Of
Length 2.00 km. The
Tension In Each Cable
Is 5.00 x 10
3
N, And
q

= 20.0
o
.


What Is The Net Work
Done On The Boat By
The Two Locomotives?

PROBLEM #2: WORK & ENERGY


A 0.075 kg Arrow Is Fired Horizontally. The
Bowstring Exerts An Average Force Of 65 N On
The Arrow Over A Distance Of 0.90 m.



With What Speed Does The Arrow Leave The
Bow?

PROBLEM #3: ENERGY


A Cyclist Approaches The Bottom Of A gradual
Hill AT A Speed Of 11 m/s. The Hill Is 5.0 m
High, And The Cyclist Estimates That She Is
Going Fast Enough To Coast Up And Over It
Without Peddling.



Ignoring Air Resistance And Friction, Find The
Speed AT Which The Cyclist Crests The Hill.

PHYSICS

Final Exam Review (Day 2)

FINAL EXAM REVIEW: DAY 2 OVERVIEW


Momentum Lecture Review


Impulse (
I =
F
net
t

=
D
p


p
f



p
i
)


Conservation Of Momentum (
P
i

= P
f
)


Collisions (
Elastic & Inelastic
)


Circular Motion (
a
c

= v
t
2
/R
)


Gravitation (
F
g

= Gm
1
m
2
/d
2
)


Problem Review (Group Problems)


Momentum


Collisions


Circular Motion

IMPULSE


When A
Large Force

Acts on An Object For A
Sufficient Amount Of Time
, Their Product Is The
Impulse

Of The Force

I =
F
net
t



The Object Will Thusly Experience A Change In
Velocity (Or
Change In Momentum
) As Shown
From Newton’s 2
nd

Law:

I =
F
net
t

=
D
p


p
f



p
i

MOMENTUM


The
Total Linear Momentum
Of An Isolated
System Remains
Constant


An
Isolated System
Is One For Which The Vector
Sum Of The
External Forces
Acting On The System
Is
Zero


P
i

= P
f

mv
1i

+ mv
2i
= mv
1f

+ mv
2f

COLLISIONS


Elastic Collision
Is One In
Which The Total KE Of The
System After The Collision
Is
Equal

To The Total KE
Before The Collision


Inelastic Collision
Is One
In Which The Total KE Of
The System After The
Collision Is
Not Equal
To
The Total KE Before The
Collision

CIRCULAR MOTION


Uniform Circular Motion Is The Motion Of An
Object Traveling At A Constant (Uniform) Speed
On A Circular Path


Even Though An Object In Circular Motion Has A
Constant Velocity (VT) It Experiences An
Acceleration Toward The Center Of The Circular
Path

a
c

= v
t
2
/R


GRAVITATION


Objects With Mass
Are Seemingly
Attracted To
Each Other

Through The
Gravitational Force


F
g

= Gm
1
m
2
/d
2



G
Is The Gravitational Constant And Has An
Experimentally Determined Value of:

G = 6.67 x 10
-
11

Nm/kg
2

PROBLEM #1: IMPULSE


During A Storm, Rain Comes
Straight Down With A Velocity Of
v
o

=
-
15 m/s

And Comes To Rest
After Impacting The Car. If The
Rain Drops Have A Mass Of
0.060 kg & It Takes 1.0s To
Come To A Rest,
What Is The
Force Exerted By The Rain On
The Car Roof?


If Hail Fell Instead Of Rain,
Would The Force On The Roof
Be Smaller Than, Equal To , Or
Greater Than That Of The
Raindrop?

PROBLEM #2: MOMENTUM


A Ball Of Mass m
1

= 0.250 kg And Velocity
v
1i

= +5.0 m/s Collides Head
-
on With A Ball Of
Mass m
2

= 0.800 kg That Is Initially At Rest.
No External Forces Act On The Balls.



If The Collision Is Elastic, What Are The
Velocities Of The Balls After The Collision?

PROBLEM #3: CIRCULAR MOTION


How Long Does It Take A Plane, Traveling At A
Constant Speed Of 110 m/s, To Fly Once
Around A Circle Whose Radius Is 2850 m?

PHYSICS

Final Exam Review (Day 3)

FINAL EXAM REVIEW: DAY 3 OVERVIEW


Kinematics Lecture Review


Displacement, Velocity & Acceleration


Speed Versus Velocity


Graphical Models Of Motion


Kinematic Equations


Freefall


2
-
D Kinematics


Horizontal Projectile Motion


Projectile Motion @ Angle



Problem Review (Group Problems)


1
-
D Kinematics


2
-
D Kinematics

DISPLACEMENT, VELOCITY & ACCELERATION


Displacement

Is A Vector That Points From An Object’s
Initial Position Toward Its Final Position (Shortest
Distance

Between Two Points)

D
x


x
f

-

x
i



Velocity

Is Defined As The Displacement (Change In
Position) Of An Object Divided By The Change In Time


v =
D
x
/
D
t



Acceleration

Is The Change In Velocity Of An Object Over
The Change In Time

a =
D
v
/
D
t



SPEED VERSUS VELOCITY


What Is Speed?


Speed Is An Average Velocity


If I Asked How Fast You Drove From Home To School
Today What Would You Say?



What About Velocity Then?


Velocity Is Instantaneous, It Changes From One
Second To The Next


Watch Your Speedometer Next Time You’re Driving!

GRAPHICAL MODELS OF MOTION


Position Versus Time (
D
xversu猠
D
t
)





Velocity Versus Time (
D
vversu猠
D
t
)

Slope =
D
x/
D
t = Velocity

Slope =
D
v/
D
t = Acceleration

D
t

D
t

D
x

D
v

KINEMATIC EQUATIONS


Kinematics

is the study of objects’ motion at
constant acceleration



There are
4 kinematic equations



Use these to
solve all 1
-
D and 2
-
D motion
problems!

KINEMATIC EQUATIONS

Equation

Formula

Relationship

#1

Velocity to Time

#2

Displacement to Time

#3

Velocity to

Displacement

#4

Average Velocity


Freefalling Bodies
Move
Freely

Under The
Influence Of
Gravity ONLY
!



The Acceleration Of An Object In Freefall Is
ALWAYS The Acceleration Of Gravity

a
g

=
-
9.81 m/s
2




Use Kinematic Equations To Solve Freefall
Problems


What Is The Acceleration Of An Object Thrown
Upwards?


What Is The Velocity Of An Object At The Peak
Of Its Motion?

FREEFALL

2
-
D KINEMATICS


Projectile Motion


Horizontal Projectile Motion


Projectile Motion At An Angle


Problem Solving Method


First Commandment Of Physics
(Keep X & Y
Directions Separate)


Solve For
Time
In
Y
-
Direction

Using A Kinematic
Equation


Use
V
ix

=
D
x
/
D
t

I渠周q
X
-
䑩rection


PROBLEM #1: GRAPHICAL MODELS

What Is The Acceleration At

The Following Points:



a). 0 to 5 s


b). 5 to 15 s


c). 15 to 20 s

PROBLEM #2: 1
-
D KINEMATICS


A Baseball Player Hits A Triple And Ends Up On
Third Base. A Baseball “Diamond” Is A Square,
Each Side Of Length 27.4 m. What is The
Magnitude Of His Displacement?



If The Same Baseball Player Rounds 2
nd

Base
With A Velocity Of 10 m/s & Slides To A Stop At
3
rd

Base, What Is His Deceleration From 2
nd

To
3
rd
?

PROBLEM #3: 2
-
D KINEMATICS


A Quarterback Throws A Pass To A Receiver,
Who Catches It At The Same Height As The
Pass Is Thrown. The Initial Velocity Of The Ball
Is 15.0 m/s, At An Angle Of 25.0
o

Above The
Horizontal. What Is The Horizontal Component
Of The Ball’s Velocity When The Receiver
Catches It?

PROBLEM #4: 2
-
D KINEMATICS


Given The Last Problem, How Far Did The
Receiver Have To Run Before Making The
Catch?

PHYSICS

Final Exam Review (Day 4)

FINAL EXAM REVIEW: DAY 4 OVERVIEW


Dynamics Lecture Review


Force Types (4 Major Forces)


Newton’s Laws Of Motion


1
st

Law (
Freebody

Diagrams
)


2
nd

Law (
S
F =
F
net

= ma
)


3
rd

Law (
F
12
=
-
F
21
)


Problem Review (Group Problems)


Net Force


Newton’s Second Law I


Newton’s Second Law II


FORCE TYPES


An
Object With Mass
(Takes Up Space) In The
Presence
Of Gravity
Has
Weight
.

W = mg


Any Object In Contact With A Surface Experiences A
Force Normal To The Surface Called The
Normal Force
(F
N
)


An
Applied Force
(Mechanical or Electrical) Is One That
Is Applied To An Object Causing It To Move (
F
A
)


The Resistive Force Acting On An Object In Contact With
Another Surface Is The Force Due To Friction


Static Friction (
F
s

=
m
s
F
N
)


Kinetic Friction (
F
k

=
m
k
F
N
)

FORCE TYPES

F
k

W

F
N

FREEBODY

DIAGRAMS


Draw The
Freebody

(The Object Separated From
Its Surroundings)


Draw Relevant Forces
Acting On The
Freebody

From The Center Of The Object


Does The Body Have
Mass In The Presence Of
Gravity?


Is The Object In
Contact With A Surface?


If Yes
, Is The Contact Surface
Frictionless

or Is
Friction

Present?


Is There An
Applied Force?


NEWTON’S SECOND LAW:
S
F

= MA


Second Law:

The
Net Force
(
F
net

=
S
F
)ActingOn⁁n
Object Will Cause The Object To
Accelerate

(
Motion
)

S
F = ma


Add Forces In Different Directions
Vectorally



F
net

2

= F
x
2

+ F
y
2

(Magnitude)



Tan (
q
) =
F
y
/
F
x

(
Direction
)

NEWTON’S 1
ST

& 3
RD

LAWS:


First Law

An
Object In Motion
Will Stay In Motion Until Acted
Upon By An External Net Force

An
Object At Rest
Will Remain At Rest Until Acted
Upon By An External Net Force


Third Law

Two Objects In Contact Will Apply Forces Equal In
Magnitude But Opposite In Direction


F
12

=
-
F
21


PROBLEM #1: NET FORCE


A Person With A Blackbelt In Karate Has A Fist
That Has A Mass Of 0.70 kg. Starting From
Rest, This Fist Attains A Velocity Of 8.0 m/s In
0.15 s. What Is The Magnitude Of The Average
Net Force Applied To The Fist To Achieve This
Level Of Performance?

PROBLEM #2: VECTOR NATURE OF 2
ND

LAW


Two Forces,
F
1

&
F
2
, Act On The 5.0 kg Block
Shown In The Drawing. The Magnitudes Of The
Forces Are F
1

= 45.0 N And F
2

= 25.0 N. What
Is The Horizontal Acceleration (Magnitude &
Direction) Of The Block?

PROBLEM #3: FRICTION


A 92 kg Baseball Player Slides Into Second
Base. The Coefficient Of Kinetic Friction
Between The Player And The Ground Is
m
k

=
0.61.



a). What Is The Magnitude Of The Frictional


Force?



b). If The Player Comes To Rest After 1.2 s,


What Is His Initial Speed?

PROBLEM #4: TENSION


Given The Following Atwood Machine With
Masses
M

and
m
,
Determine The Acceleration
Of Mass m
.

m