Download Packet #2 Why Do Objects Move?

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Class
Date
Packet #2
Why Do Objects Move?
1-1 What is Motion?
YOU WILL LEARN:
o To identify the relationship between motion and a reference
point.
o To describe the motion of an object by its position, direction
of motion, and speed.
o To determine the speed and acceleration of a moving object.
Key Terms
motion: an object’s change in position over time when compared with a reference point
speed: the rate at which an object moves; speed depends on the distance traveled and the time taken to
travel that distance
velocity: the speed of an object in a particular direction
acceleration: the rate at which speed changes; an object accelerates if its speed changes, if its direction
changes, or if both its speed and its direction change
Lesson Summary
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The motion of an object is always observed in relation to another object that appears to stay in place.
The object that appears to stay in place is a reference point.
Motion is described with a reference direction, such as north, south, east, west, or up and down.
The speed of an object is the distance traveled and the time needed to travel that distance.
The acceleration of an object is the change in speed during a given amount of time.
Find and observe a moving object. What are you using as the reference point?
1-2 What is a force?
YOU WILL LEARN:
o To identify examples of forces in nature.
o To predict and describe the effect of all forces acting on an
object.
o To determine the net force on an object.
o To identify balanced and unbalanced forces and to describe
their effects.
Key Terms
force: a push or a pull
balanced forces: forces that are equal in size but opposite in direction
unbalanced forces: forces that cause a change in the motion of an object
Lesson Summary
• A force is a push or a pull.
Concepts and Challenges in Physical Science, Teacher’s Resources CD-ROM
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Force: CHAPTER 12
Lesson Notes, page 1
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Forces that are equal in size and opposite in direction are called balanced forces.
Unbalanced forces change the motion of an object.
When unbalanced forces act on an object at rest, the object will move.
When unbalanced forces act on a moving object, the motion of the object will change. The object may
speed up, slowdown, stop moving, or change direction.
What are some examples of force that you use every day?
1-3 What is friction?
YOU WILL LEARN:
o
To identify the direction of the force of friction during the
motion of an object.
o
To predict ways to change friction.
Key Terms
friction: force that opposes the motion of an object
lubricants (LOO-brih-kuhnts): materials that reduce friction
Lesson Summary
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To stop a moving object, a force must act in the direction opposite to the direction of motion.
A force that opposes the motion of an object is called friction.
Some examples of friction include sliding friction, air resistance, and rolling friction.
Force is needed to overcome the force of friction.
Reducing friction makes it easier to move an object.
One way to reduce friction is to change sliding friction to rolling friction.
Friction can be reduced by using lubricants.
What is an example of a situation that you might want to increase friction?
1-4 What is gravity?
YOU WILL LEARN:
o
To explain the law of universal gravitation.
o
To determine the gravitational force on objects given the mass
of the objects and the distance between the objects.
o
To describe the difference between mass and weight.
Key Terms
gravity: force of attraction between all objects in the universe
weight: a measure of the gravitational force exerted on an object, usually by Earth
mass: the amount of matter that something is made of
Lesson Summary
• The law of universal gravitation states that all objects in the universe are attracted to one another
because of the force of gravity between them.
• The amount of gravitational force between two objects depends on the mass of each object.
• The force of gravity between two objects decreases as the distance between them increases.
Concepts and Challenges in Physical Science, Teacher’s Resources CD-ROM
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Force: CHAPTER 12
Lesson Notes, page 2
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Class
Date
Weight changes when gravitational force changes, mass does not.
The moon’s gravitational force is less than the Earth’s. Does your mass or weight change
when you are on the moon?
Explain:
2-1 How does gravity affect motion?
YOU WILL LEARN:
o To identify the forces acting upon a falling object.
o To identify the forces acting upon an orbiting object.
o To identify the forces acting upon a projectile.
Key Terms
Free fall: the condition an object is in when gravity is the only force acting on it
Projectile motion: the curved path an object follows when thrown or propelled near the surface of
Earth
Lesson Summary
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All objects accelerate toward Earth at 9.8 m/s/s.
Air resistance (fluid friction) slows the acceleration of falling objects.
An object is in free fall only if gravity is the only force acting on it.
An orbit is formed by combining forward motion and free fall.
Projectile motion has two components: horizontal and vertical. Gravity affects only the vertical
motion of projectile motion.
What type of motion keeps the Earth and other planets from flying off into space?
2-2 What are Newton’s Laws of Motion?
YOU WILL LEARN:
o To apply Newton’s 3 Laws of Motion to explain and predict
changes in an object’s motion.
o To recognize and explain the Law of Conservation of
Momentum.
Key Terms
inertia: the tendency of all objects to resist any change in motion
momentum: a property of a moving object that depends on the object’s mass and velocity
Lesson Summary
• Newton’s first law of motion states that the motion of an object will not change if no unbalanced
forces act on it.
• Inertia is the tendency of matter to resist a change in motion. Mass is a measure of inertia..
• Newton’s second law of motion states that the acceleration of an object depends on its mass and the
force exerted on it. F=MxA
Force = Mass x Acceleration
Concepts and Challenges in Physical Science, Teacher’s Resources CD-ROM
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Force: CHAPTER 12
Lesson Notes, page 3
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Class
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• Newton’s third law of motion states that whenever one object exerts a force on a second object, the
second object exerts an equal and opposite force on the first.
• When two or more objects interact, momentum may be exchanged, but the total amount of
momentum does not change. This is the law of conservation of momentum.
As you sit on your chair, the pull of Earth’s gravitational force wants to pull you down, why
do you stop at the chair?
What allows a plane to fly?
YOU WILL LEARN:
o
To recognize and explain Bernoulli’s principal.
o
To identify the 4 forces acting on an airplane in flight.
Key Terms
Air pressure: pressure caused by the force exerted by Earth’s atmosphere
Bernoulli’s Principle: as the speed of a fluid (air) increases, its pressure decreases.
Lesson Summary
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The force of air molecules that are pulled toward Earth’s center by gravity is called air pressure.
Air pressure is greatest near Earth’s surface and decreases with altitude.
Bernoulli’s principle states that as the speed of a fluid (air) increases, the pressure it exerts decreases.
Airplane wings use Bernoulli’s principle to lift the plane.
The four forces acting upon an airplane are Lift (Bernoulli’s principal), Air Resistance (fluid
friction), Gravity, and Thrust.
What would happen to an airplane if the air resistance (fluid friction) increased?
Concepts and Challenges in Physical Science, Teacher’s Resources CD-ROM
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Force: CHAPTER 12
Lesson Notes, page 4
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Class
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Why Do Objects Move?
Using the 3 Step Method
1. Write the formula:
Speed
=
Distance
------------Time
2. Substitute numbers & units and solve the formula (Complete the same math on the
units as you did on the numbers):
Speed
3. Write the answer with the unit:
25 meters
---------------5 seconds
=
Speed =
What if you need to find the Distance or Time?
1. Write the formula you are given
Speed
=
Distance
------------Time
Or
S
=
D
------------T
2. Substitute the numbers and units that you have.
S
=
D
------------T
5 m/s
=
D
------------5s
3. Solve the equation for the unknown variable using basic math skills.
D
=
5 m/s x 5 s
Concepts and Challenges in Physical Science, Teacher’s Resources CD-ROM
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Force: CHAPTER 12
Lesson Notes, page 5
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Class
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Speed = __________________________________________________
Any point in time
Speed
=
Distance
------------Time
Average over time
Average Speed
=
Total Distance
------------Total Time
Example: Using the wind up toy car, measure the time it takes the car to
travel 1 meter. Calculate the average speed.
Distance =
Time =
1.
2.
3.
Example: Try the experiment again using a smaller distance of your choice.
Distance =
Time =
1.
2.
3.
Concepts and Challenges in Physical Science, Teacher’s Resources CD-ROM
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Force: CHAPTER 12
Lesson Notes, page 6
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As Time
, the Distance
.
What is the story of the graph? Look carefully at the x – axis and the y –
axis. What variable are they showing you? Are the numbers increasing
or decreasing? Begin with the x-axis and tell the STORY of the GRAPH.
Name
Class
Date
Force: CHAPTER 12
Lesson Notes, page 7
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Date
Acceleration =
Acceleration =
Final Speed – Starting Speed
------------Time
Example: A car heads north at 50 meters/sec. After 30 seconds it is going
75 meters/sec. What is its acceleration? (use 3 Step Method)
Final Speed =
Time =
Starting Speed =
1.
2.
3.
Concepts and Challenges in Physical Science, Teacher’s Resources CD-ROM
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Force: CHAPTER 12
Lesson Notes, page 8
, the
.
Date
As
Class
What is the story of the graph? Look carefully at the x – axis and the y –
axis. What variable are they showing you? Are the numbers increasing
or decreasing? Begin with the x-axis and tell the STORY of the GRAPH.
Name
Note: Velocity and
Speed are the same.
Concepts and Challenges in Physical Science, Teacher’s Resources CD-ROM
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Force: CHAPTER 12
Lesson Notes, page 9
Name
Class
Date
Force = __________________________________________________
Unit = Newton
Net Force = The sum of all forces on an object.
Example:
+
50 N
=
30 N
80 N
Balanced Force = When the sum of all the forces are equal but opposite
in direction. The result will be no movement.
Example:
+
75 N
=
75 N
_________ N
Unbalanced Force = When the forces are not equal and motion occurs.
Example:
+
40 N
=
35 N
+
75 N
________ N
=
25 N
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_________ N
Force: CHAPTER 12
Lesson Notes, page 10
Name
Class
Concepts and Challenges in Physical Science, Teacher’s Resources CD-ROM
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Date
Force: CHAPTER 12
Lesson Notes, page 11
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Class
Date
Friction = The Force that ALWAYS Opposes Motion.
There are 4 types of friction:
1. Sliding
Draw/write an example:
2. Rolling
Draw/write an example:
3. Fluid (gas or liquid)
Draw/write an example:
4. Static
Draw/write an example:
Concepts and Challenges in Physical Science, Teacher’s Resources CD-ROM
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Force: CHAPTER 12
Lesson Notes, page 12
Concepts and Challenges in Physical Science, Teacher’s Resources CD-ROM
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Date
Summarize in your own words:
Class
What are the rules (3) of GRAVITY?
Name
Force: CHAPTER 12
Lesson Notes, page 13
Name
Class
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Force: CHAPTER 12
Lesson Notes, page 14
Name
Class
Date
Gravitational Force
Enrichment Activity for Lesson 1-4
Skills: interpreting diagrams
The diagrams below illustrate several important properties of gravitational force.
In each picture, the sizes of the arrows are proportional to the size of the forces
between the objects. Assume that the larger the size of the object, the larger its
mass. Study the diagrams. Then, answer the questions.
1. Look at Figures A and B. What is the same in both pictures? __________________________________
2. How do Figures A and B differ? ___________________________________________________________
_______________________________________________________________________________________
3. What important property of gravitational force is illustrated by Figures A and B? ________________
_______________________________________________________________________________________
4. Look at Figure C. How are the three pairs of objects different? _________________________________
_______________________________________________________________________________________
5. What property of gravitational force is illustrated by Figure C? ________________________________
_______________________________________________________________________________________
6. How do the two objects in Figure D differ from each other? ___________________________________
_______________________________________________________________________________________
7. What does Figure D tell you about gravitational force? _______________________________________
_______________________________________________________________________________________
8. Which diagram is most like the situation that exists when an apple falls to the ground? Why?
_______________________________________________________________________________________
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Force: CHAPTER 12
Lesson Notes, page 15
Name
Class
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Date
Force: CHAPTER 12
Lesson Notes, page 16
Name
Class
How are
Date
?
1.Where is the astronaut in each diagram? (write the location on each diagram)
2. How does Earth’s gravity compare with the moon’s?
How do you know?
4.What changed for the astronaut from the Earth to the moon?
Why?
5. What did not change for the astronaut from the Earth to the moon?
Why?
Weight is
Mass is
Concepts and Challenges in Physical Science, Teacher’s Resources CD-ROM
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Force: CHAPTER 12
Lesson Notes, page 17
Name
Class
Date
Newton’s Laws
Newton’s First Law of Motion:
An object at REST will remain at REST and an object in MOTION will remain in
MOTION at a constant SPEED unless an OUTSIDE FORCE acts upon it.
Newton’s first law of motion describes how OUTSIDE forces act upon an object.
Newton’s Second Law of Motion:
FORCE = MASS x ACCELERATION
Newton’s second law of motion describes how a moving object’s MASS and ACCELERATION
is directly related to the FORCE needed to move that object.
The unit for force is the NEWTON
1 Newton = 1 kilogram x 1 m/sec/sec
Newton’s Third Law of Motion:
For every ACTION there is a equal and opposite REACTION.
Forces always occur in PAIRS.
Example of Newton’s third law of motion: The MOMENTUM BALL APPARATIS.
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Force: CHAPTER 12
Lesson Notes, page 18
Name
Class
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Date
Force: CHAPTER 12
Lesson Notes, page 19