Introduction: Category 2

1
Introduction Category 2 Force, Motion and
Energy
Balanced and Unbalanced Force
Speed, Velocity and Acceleration
Newtons Laws..
1st Law Law of Inertia
2nd Law Force and Acceleration
3rd Law Action-Reaction
Work Force x Distance
How much work is being done?
Potential and Kinetic Energy
Calculate average speed
Energy Transformations
2
Force Facts

• Forces are measured in Newtons (N)
• Forces ALWAYS act in pairs
• Each force in the pair acts in opposite
  directions

3
Types of Force

• There are many different kinds of force. There
  are pushes
• and pulls
• electromagnetic forces
• weak forces
• strong forces
• and gravitational forces,
• Some forces are referred to as contact forces and
  some are non-contact forces

4
Force and Motion

• A FORCE is any action that can cause a
• change in motion

PULL
PUSH
A force is a PUSH or a PULL!
5
Balanced Forces

• When the forces acting on an object are
  BALANCED, NO change in motion occurs
• The forces in each direction are equal so they
  cancel each other out

6
Unbalanced Forces

• When the forces acting an object are UNBALANCED,
  a change in motion occurs
• One force is larger than another

7
Combined Forces

• The direction of two force matters!

Forces can combine by addition
8
Types of Motion

• Speed
• Velocity
• Acceleration

9
Types of Motion SPEED

• SPEED is the distance an object moves in a
  given amount of time
• Speed measures the RATE of motion
• Speed Distance s d
• Time t
• Units distance unit/time unit
• km/hr
• m/s
• mi/hr

10
Speed Calculations

• Calculation Triangle
• How to use it
• Cover up the variable you are solving for
• Horizontal line means divide
• Vertical line means multiply

11

• Try to solve this
• It takes a baseball 35 seconds to travel
  from the mound to homeplate. What is the speed of
  the ball to travel the18.4 m from the pitchers
  mound to home plate?

Formula I Will Use
s d t
Variables Im Given T 35 s d 18.4 m
What Im Looking for speed
The Solution to my problem is
s 18.4 m 35 s
.5 m/s
12
Changes in motion can be measured and graphed
Examine the graph provided. The graph shows the
speed of a car traveling east over a 12 second
period on a flat surface. In the first 6 seconds
shown on the graph, the car is
INCREASING ITS SPEED
13
Types of Motion VELOCITY

• VELOCITY - is speed in a particular direction
• Velocity distance v d
• time t
• Units speed direction
• 50 mi/hr north
• 36 m/s from Dallas to Houston
• This basically the same calculation as speed,
  just add a direction!!

14
Example Problem

• The cheetah, the fastest of land animals,
  can run a distance of 274 m in 8.65 sec. at its
  top speed. If the cheetah is running north, what
  is its velocity?

Variables Im Given d 274 m t 8.65 s
Formula I Will Use v
d t
What Im Looking for velocity
The Solution to my problem is
v 274 m 8.65 s
31.7 m/s
NORTH
15
Types of Motion Acceleration

• Acceleration is a change in speed or direction of
  an object.
• Which is another way to say change in VELOCITY !
• There are only 3 ways to accelerate
• Speeds up
• Slows down (deceleration)
• Changes direction

16
Acceleration
17

• If an object is traveling at a constant speed
  but is going in a circle, it is accelerating
  because its direction is changing

18
Are these objects accelerating? Explain.
Yes, there is either a change of direction or
speed!
19

• Force, Speed, and Motion
• How are they related?

20
Newtons 3 Laws

• 1st Law of Inertia
• 2nd Law of Force Acceleration
• 3rd Law of Action-Reaction

21
Newtons First Law of Motion

• What the law states An object at rest will
  remain at rest and an object in motion will
  remain in motion at a constant velocity until it
  experiences an unbalanced force
• Also known as the Law of Inertia
• Describes motion produced by BALANCED FORCES

22
INERTIA is an objects resistance
to changes in motion
From the Latin word iners meaning lazy
An object at rest also has inertia it wants to
stay at rest!
A moving object has inertia it wants to keep
moving!
23
First Law

• Study the driver without a seatbelt to
  understand this better!
• What is the unbalanced force?
• The wall
• What happens to the driver?
• He keeps going forward since only the car
  experienced an unbalanced force

24
Newtons Second Law of Motion

• What the law states Acceleration is
• produced when an UNBALANCED
• FORCE acts on a MASS
• The greater the mass of the object the greater
  the amount of force needed to accelerate the
  object
• Describes motion produced by UNBALANCED FORCES
• OKAY BUT WHAT DOES THIS MEAN
• EXACTLY???

25
Newtons Second Law
Little Acceleration
Little Force
Same Mass
Big Force
Big Acceleration
26
Small Mass / Big Acceleration
Same Force
Big Mass / Small Acceleration
27
The Math Behind the Law

• The Second Law shows the relationship
• between force, mass, and acceleration
• It can be expressed as a mathematical equation
• F maor FORCE MASS x ACCELERATION

28
Everyone unconsciously knows this law!!

• You know that heavier objects require more
• force to move the same distance as lighter
• objects.

                                                     
                                                            
29

• Fma is Newtons 2nd Law and can be stated A
  net force is equal to the mass of the object
  times its acceleration. Therefore if equal force
  is applied to two objects of different mass, the
  smaller mass will accelerate more

30
Newtons Third Law of Motion

• What the law states For every ACTION there is
  an equal and opposite REACTION
• ACTION and REACTION are names of FORCES!!
• Forces ALWAYS come in pairs

31
Action Reaction Forces

• Since a force (push or pull) is an interaction
  between objects, two objects are involved in
  every force. Lets call the objects A and B
• Action force
• A pulls/pushes B
• Reaction force
• B pulls/pushes A

32
Identifying Action and Reaction Forces

• Your hand pushing against a wall
• Action?
• Your hand pushes to the left on the wall
• Reaction?
• The wall pushes to right on your hand

33
Is it WORK or not?
34
Formula for work

• Work Force x Distance
• The unit of force is newtons
• The unit of distance is meters
• The unit of work is newton-meters
• One newton-meter is equal to one joule
• So, the unit of work is a joule

35
WFD

• Work Force x Distance
• Calculate If a man pushes a concrete block 10
  meters with a force of 20 N, how much work has he
  done?
• 200 joules
• (W 20N x 10m)

36
Simple Machines

• Wedge

Screw
37
Machines Can

• Make work EASIER to accomplish (but amount is the
  same)
• Change magnitude of force required to accomplish
  task
• Change direction of force required to accomplish
  task

38
Machines Cannot

• Decrease the amount of work necessary to
  accomplish a given task
• Have 100 efficiency
• Run perpetually

39
Forms of
Energy
40
Energy is the ability to cause change
41
POTENTIAL ENERGY

• Energy an object has because of its position
• (Stored Energy)

42
KINETIC ENERGY

• Energy of motion. Only a moving object has
  kinetic energy
• Amount of energy depends on speed and mass

43
EXAMPLE 1
POSITION 1
Potential Energy
The boulder at the top of the hill has potential
energy and no kinetic energy.
POSITION 2
Kinetic Energy
Potential Energy
As the boulder rolls down the hill, the potential
energy transforms into kinetic energy and kinetic
energy becomes greater until
POSITION 3
The boulder is in a resting position with low
potential energy and no kinetic energy.
44
Energy vs. Matter everything on Earth is either
energy or matter

• Energy has no mass or weight
• Energy does not take up space
• Energy is NOT
• matter

• Matter has mass
• and weight
• Matter takes up
• space
• Matter is NOT
• energy

45
THERMAL ENERGY

• energy due to molecular movement within an
  object
• increased temperature increased thermal
  energy

46
Which of these objects has more thermal energy?
47
CHEMICAL ENERGY

• Chemical energy is stored in chemical bonds.
  When molecules are broken apart energy is
  released.

48
Each of these items contains chemical energy.
49
LIGHT ENERGY

• Energy carried by light is called radiant
  energy.
• Light energy travels at a speed of 300,000 km/s.

50
ELECTRICAL ENERGY

• energy of electrons
• moving along a path
• (electrical current)

51
NUCLEAR ENERGY

• energy stored in the
• nucleus of an atom

52
Examples of Energy Transformations
Your body converts chemical energy in food into
energy .
it needs to move,think,grow and heat the body.
53
Examples of Energy Transformations
54
Forces related to basic processes

• Blood flow in the body
• Plate movement (tectonics)
• Volcanic eruptions
• Earthquakes
• Mountain building
• Emergence of seedlings
• Erosion

55
Blood Flow
56
(No Transcript)
57
Volcanic Eruptions
58
Hilo, Hawaii
59
(No Transcript)
60
Mountain Building
61
(No Transcript)
62
Emergence of Seedlings
63
(No Transcript)
64
(No Transcript)
65
Erosion
66
(No Transcript)
67
(No Transcript)
68
Check your understanding
69

• 1. Which of the following units would most
  accurately describe velocity?
• Hours, south
• Meters per second, south
• Meters per second
• Meters, south

70
The boulder would have the greatest kinetic
energy at which of the positions on the waterfall?
A position 1 B position 2 C position 3 D
position 4
B
71
A yo-yo can demonstrate both potential and
kinetic energy. When does a yo-yo have it
greatest potential energy?
A In the hand before the yo-yo is
releasedB At the bottom of the stringC When
the yo-yo is fallingD When the yo-yo is
climbing the string
72

• 4. Which of the following is an example of a
  wave?
• a. erosion
• b. an earthquake
• c. a volcano
• d. a glacier

73

• 5. Windmill farms are becoming a popular method
  of generating electricity for some communities.
  What form of energy in wind is used to turn the
  giant blades of the windmill?
• Chemical
• Mechanical
• Electrical
• Thermal

74

• In a nuclear reactor, the energy used to turn
  water into steam is in what form?
• A. Chemical
• B. Nuclear
• C. Electrical
• D. Thermal

75
7. Which of the following can be used to
transform chemical energy into heat energy?

• melting a candle
• B. lighting a match
• C. solar panels
• D. light bulb

Answer B
76
When the human heart contracts, it pumps blood to
other parts of the body. When the heart
contracts, the blood moves because the--

1. Pressure to the heart increases
2. Temperature of the blood increases
3. Density of the blood increases
4. Size of the heart increases

77
As a lima bean seedling starts to grow into the
soil the root tip is able to push through the
soil because it acts as a --

1. Wheel
2. Pulley
3. Gear
4. Wedge

78
Which force causes the water to move downstream?

1. Gravitational
2. Chemical
3. Electrical
4. Solar

79
11. Which of the following describes the motion
of the runner?
A The runner is moving at a constant rate B The
runner is moving slower at the end C The runner
is speeding up D The runners speed was a
constant 4 m/s