7th Grade Science
http://academic.brooklyn.cuny.edu/history/virtual/portrait.htm
http://people.deas.harvard.edu/~jones/ap216/images/bandgap_engineering/periodic_table.gif
© Fall 2005, Pflugerville ISD, 7th Grade
7th Grade Science
PISD PowerPoint Lessons
Developed By
Lori More, Park Crest Middle School
Edited By
Kenn Heydrick, Coordinator of Science & Health
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1:
Physical Science
Chapter 2: Elements, Compounds, and Mixtures
Section 1: Elements
Section 2: Compounds
Chapter 3: Introduction to the Periodic Table
Section 1: Arranging the Elements
Section 2: Classifying the Elements
Chapter 4: Forces in Motion
Section 1: Gravity and Motion
Section 2: Newton’s Laws of Motion
Chapter 5: Work and Machines (Focus on Section 3)
Section 3: Types of Machines
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements, Compounds, and Mixtures
What Do You Think?
How is an element
different from a
compound?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Answer
An element is
made up of only
one pure
substance, and a
compound is
composed of two
or more elements
that are
chemically
combined.
© Fall 2005, Pflugerville ISD, 7th Grade
Gold
http://www.worldofrockhounds.com/huge-gold-nugget-sm.JPG
Water
http://www.nbmg.unr.edu/slides/water/5.htm
Unit 1
Elements
An element is a pure
substance that cannot be
separated into simpler
substances by physical or
chemical means.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements
A pure substance is a substance
in which every particle of that
element is the same.
– Example: Every particle in a 5g gold
nugget is like every other particle of gold,
no matter where they are found.
http://www.libertarian.nl/NL/archives/01-gold-bar.jpg
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements
Every element has a unique
set of properties.
The Periodic Table of Elements
is arranged according to these
properties.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements
Every element has a unique
set of properties.
Some physical properties that
are used to classify elements
are boiling point, melting point,
color, and density.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements
Chemical properties
used to separate
elements from each
other include reactivity
with acids, or reactivity
with oxygen.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements Are Grouped
Some elements are shiny, and
can conduct thermal energy.
They are all grouped together
on the left hand side of the
Periodic Table. They are called
metals. Not all metals are
exactly alike, but they do have
some properties in common.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements
Elements Can Be Identified By
Categories
If you know the category, you know the
properties.
1. Share with your class how
CDs can be classified by
categories?
2. How can dogs be
classified by categories?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements
Elements
are
identified
by 3 main
categories
© Fall 2005, Pflugerville ISD, 7th Grade
• Metals
• Nonmetals
• Metalloids
Unit 1
Elements
Metals
Metals are elements
that are usually
shiny and good
conductors of
electricity and heat.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements
Metals
Metals are also
malleable (can be
hammered into thin
sheets).
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements
• Metals are ductile, or can
be drawn into thin wires.
• Metals are located to the
left of the “zig zag line” on
the Periodic Table.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements
• Examples: Iron (Fe) and
Copper (Cu).
http://www.flamo.net/crystals/iron.jpg
© Fall 2005, Pflugerville ISD, 7th Grade
http://resourcescommittee.house.gov/subcommittees/emr/usgsweb/materials/copper.html
Unit 1
Elements
Click below to see properties of Metals.
http://www5.unitedstreaming.com/index.cfm
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements
Nonmetals
• Usually dull and poor conductors
of heat and electric current.
• Tend to be brittle and unmalleable.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements
Nonmetals
• Nonmetals are located to the
right of the “zig zag line” on
the Periodic Table.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements
Nonmetals
• Examples: Neon (Ne) and
Carbon (C)
reluctant-messenger.com/ diamond_sutra.htm
www.neonstreet.com/ sign2.html
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements
Click below to see properties of Nonmetals
http://www5.unitedstreaming.com/index.cfm
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements
Metalloids
Share properties of both
metals and nonmetals.
• Can be shiny or dull.
• Somewhat malleable and
ductile.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements
• Metalloids touch the “zig zag
line” on the Periodic Table.
• Examples:
Silicon (Si)
Arsenic (As).
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements
Click below to see properties of metalloids.
http://www5.unitedstreaming.com/index.cfm
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Let’s Review!
-1-
Describe some physical
properties of the element iron.
http://neil.fraser.name/news/2004/05/22/
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Answer
Physical properties include:
1. Melting Point: 1535 °C
2. Density: 7.9 g/cm3
3. Iron has the ability to conduct heat
and electrical current.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Let’s Review
-2-
What is an example of a
metal that is very
malleable, shiny, and is
used often in kitchens?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Answer
Aluminum Foil
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Compounds
What Do You Think?
What do salt, sugar,
baking soda, and
water have in
common?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Compounds
A compound is a pure substance
composed of two or more elements
that are chemically combined.
Familiar Compound
Compound
Elements Combined
Table Salt
Sodium and Chlorine
Water
Hydrogen and Oxygen
Sugar
Carbon, Hydrogen, and Oxygen
Carbon Dioxide
Carbon and Oxygen
Baking Soda
Sodium, Hydrogen, Carbon, and Oxygen
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Compounds
Properties of Compounds
• Compounds, like elements, can be
identified by their own physical and
chemical properties.
• What are some examples of
physical and chemical properties?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Compounds
Each compound has different properties
than the elements that make them up.
Water
Hydrogen
Oxygen
Melting Point
0°C
-259.14 °C
-218.4 °C
Boiling Point
100 °C
-252.87 °C
-183.0 °C
1.0 g/cm3
0.08988 g/cm3
1.429 g/cm3
Liquid
Gas
Gas
Density
State at Room Temperature
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Compounds
Compounds are
Composed of
Elements.
The compound Water is
composed of Hydrogen
and Oxygen chemically
bonded together.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Compounds
Compounds are Composed
of Elements.
• The compound Ammonium is
composed of Nitrogen and
Hydrogen chemically bonded
together.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Compounds
Click below to see a video clip of sodium metal
and chlorine gas being combined.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Let’s Review!
-1What is the difference
between an element and a
compound?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Answer
• An element is a pure substance that
cannot be separated into simpler
means by physical or chemical means.
• A compound is a pure substance
composed of two or more elements that
can be broken into simpler substances
by a chemical change.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Compounds
Make a Venn diagram comparing and
contrasting elements and compounds.
Elements Compounds
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements, Compounds, and
Mixtures
Pre-AP Extensions for Chapter 2
• Mixtures are combinations of two or
more elements that are not chemically
combined.
• Mixtures can be separated into 2 types:
homogenous mixtures and
heterogenous mixtures.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements, Compounds, and
Mixtures
Homogenous Mixtures
• A homogenous mixture is a mixture of
two or more substances that is
completely uniform in composition.
• Homogenous mixtures can be separated
by physical means, but it is often difficult
to do.
• Examples include salt water, kool aid, and
air.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements, Compounds, and
Mixtures
Heterogenous Mixtures
• A heterogenous mixture consists of
many different items, which are often
not easily sorted or separated, though
they are clearly distinct.
• Examples include oil and water mixed
together, sand or gravel, and even
chocolate chip cookies!
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Elements, Compounds, and
Mixtures
Websites to Visit
• Percent Calculations in a Mixture
• Chromatography Mixtures Lab
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
What Do You Think?
How do scientists use
physical properties to
arrange elements on the
periodic table?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
Dimitri Mendeleev
discovered a
pattern to the
elements in the
periodic table in
1869.
www.astrosurf.org/lombry/ quantique-histoire.htm
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
He simply wrote the
names of all of the
elements on cards,
along with some of
their properties.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
• Mendeleev tried arranging his
cards based on different
properties like color, density,
melting point, and atomic mass.
• He found that by arranging the
elements by increasing atomic
mass, he found many other
properties that fit a pattern.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
Mendeleev found that by arranging the
elements by increasing atomic mass,
similar physical and chemical properties
repeated in every 8th element.
This is called periodic, or having a
regular, repeating pattern.
Can you think of anything else that is
periodic?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Let’s Review!
-1-
Why was Mendeleev so
important in the study of the
periodic table?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Answer
• Mendeleev was responsible
for arranging the periodic
table by increasing atomic
mass.
• This arrangement organizes
the table making it easier for
us to use.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
What Do You Think?
How do scientists use
physical properties to
arrange elements on the
periodic table?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
Elements are classified on
the periodic table based on
their properties.
• Like we learned in Chapter 2,
we classify them as metals,
nonmetals, and metalloids.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
Metals
Remember that
metals are shiny,
ductile, malleable,
and are good
conductors of
thermal energy
and electrical
current.
http://shawnee.noacsc.org/highschool/departments/teachers/pages/mikel/periodictable.html
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
Metals
Metals are
located to
the left of
the “zig
zag” line on
the periodic
table.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
Physical Properties of Metals
Go.hrw.com
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
Chemical Properties of Metals
Go.hrw.com
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
Nonmetals
Remember also
that nonmetals
are not shiny
and are poor
conductors of
thermal energy
and electric
current.
http://shawnee.noacsc.org/highschool/departments/teachers/pages/mikel/periodictable.html
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
Nonmetals
Nonmetals
are found to
the right of
the “zig zag”
line on the
periodic
table.
http://shawnee.noacsc.org/highschool/departments/teachers/pages/mikel/periodictable.html
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
Physical and Chemical Properties of Nonmetals
Go.hrw.com
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
Metalloids are
elements that
have properties
of both metals
and nonmetals.
Metalloids
http://shawnee.noacsc.org/highschool/departments/teachers/pages/mikel/periodictable.html
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
Metalloids
© Fall 2005, Pflugerville ISD, 7th Grade
Metalloids
border the
“zig zag” line
on the
periodic
table.
Unit 1
Introduction to the Periodic Table
Physical and Chemical Properties of Metalloids
Go.hrw.com
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Let’s Review!
-1-
Use the properties of
metalloids to explain
their position on the
periodic table.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Answer
• Metalloids are located
between metals and
nonmetals because they
have properties in between
metal and nonmetals.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
Pre-AP Extensions for Chapter 3
• There are trends in Metallic and
Nonmetallic Character that we can
see on the periodic table.
• Metallic character is strongest for
the elements in the leftmost part of
the periodic table, and tends to
decrease as we move to the right in
any period.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
• Within any group of elements
(columns), the metallic character
increases from top to bottom . This
general trend is not necessarily
observed with the transition
metals.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Introduction to the Periodic Table
Pre-AP Extensions for Chapter 3
http://wine1.sb.fsu.edu/chm1045/notes/Periodic/Metals/Period06.htm
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
What Do You Think?
How does the force of
gravity affect falling
objects?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Gravity
causes all
objects to fall
toward the
ground with
the same
acceleration,
9.8 m/s2.
© Fall 2005, Pflugerville ISD, 7th Grade
http://mired.org/home/mwm/parachuting/floating2.jpeg
Unit 1
Forces in Motion
A little vocabulary before we start…
• Force- a push or a pull
• Velocity- the speed of an object
and its direction of motion.
• Acceleration- the rate at which
the velocity changes.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Activity
Drop a tennis ball and a golf
ball from a table at the same
height at the same time.
Which hits the ground first?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
• In the late 1500s, Galileo
found that mass does not
affect the time the object
takes to fall to the ground.
• Both the elephant and the
feather hit the ground at the
same time.
• This only happens if there is
NO air resistance.
http://www.physicsclassroom.com/mmedia/newtlaws/efff.html
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Air resistance is a fluid
friction that opposes the
motion of object through the
air.
It slows down acceleration.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Drop 2 sheets of paper- one
crumpled in a tight ball and the
other kept flat.
What happens? Why?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Air resistance is affected by:
• The Size of the object
• The Shape of the object
• The Velocity of the object
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
This is what
happens to the
elephant and
feather when air
resistance is
present.
http://www.physicsclassroom.com/mmedia/newtlaws/efarm.htl
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
An object is in free fall only if
gravity is pulling it down and
no other forces are acting on it.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
• Because air resistance is a force, free
fall can only occur where there is no
air, such as a vacuum (a place in
which there is no matter) or in space.
• If the feather and the elephant were in
free fall, they would hit the ground at
the same time.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
• Astronauts appear to be
“weightless” in space because of
free fall.
• Both the astronaut and the space
shuttle are falling toward the earth
at the same rate.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
How an orbit is formed
Go.hrw,com
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Projectile Motion is the
curved path an object follows
when it is thrown or
propelled near the surface of
the Earth.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Projectile motion has 2
components: horizontal and
vertical.
- When throwing a ball, horizontal
motion occurs when the ball leaves your
hand.
- After the ball leaves your hand, gravity
pulls it down giving it vertical motion.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Projectile Motion from a Baseball
Go.hrw.com
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Let’s Review!
-1-
Using a baseball as an example,
name three instances in which
this sport illustrates projectile
motion.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Answer
Baseball illustrates
projectile motion when a
player throws the ball,
when a player hits the ball,
and a player demonstrates
projectile motion when he
dives to catch the ball.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
What Do You Think?
Explain what you know
about Newton’s Laws of
Motion.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Newton’s Laws of Motion
In 1686, Sir Isaac
Newton explained the
relationship between
force and motion
with his three laws of
motion.
© Fall 2005, Pflugerville ISD, 7th Grade
http://academic.brooklyn.cuny.edu/history/virtual/portrait.htm
Unit 1
Forces in Motion
Newton’s First Law of Motion
1. An object at rest remains at rest until its
acted on by an unbalanced force.
2. An object stays in motion at the same
speed and in the same direction until its
acted on by an unbalanced force.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
How does this illustrate
Newton’s First Law?
http://www.physicsclassroom.com/mmedia/newtlaws/efarm.htl
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Newton’s First Law is also called
the Law of Inertia.
Inertia is the tendency of all
objects to resist any change
in motion.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Newton’s First Law is also called
the Law of Inertia.
Example…your mom makes a
sharp left turn in the car…you
slide toward the door.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Newton’s Second Law of Motion
If you are applying the same
force on an object, an objects
acceleration decreases as its
mass increases.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Newton’s Second Law of Motion
When applying the same force
on an object, as an
acceleration increases, its
mass decreases.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Newton’s Second Law continued…
• An object’s acceleration
increases as the force on the
object increases
• An object’s acceleration
decreases as the force on an
object decreases.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Activity
Tell your neighbor 2
ways a grocery store
shopping cart could
illustrate Newton’s
Second Law?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Click on the video below to see
examples of Newton’s Second Law
http://www5.unitedstreaming.com/index.cfm
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Newton’s Third Law of Motion
• All forces act in pairs.
• If a force is exerted, another
force is exerted that is equal in
size, but opposite in direction to
the first force.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Click below to see examples of
Newton’s Third Law
http://www5.unitedstreaming.com/index.cfm
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Newton’s Third Law also deals with
momentum
• Momentum is a property of a moving
object.
• Momentum depends on the objects
mass and velocity.
• If a small car and a large truck are both
traveling down the highway at the same
velocity, the truck has more mass,
therefore it will have more momentum.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Momentum is Conserved
When a moving object hits
another object, the
momentum of the first
object transfers to the
second object.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Momentum is Conserved
• Example:
–When one pool ball hits another
pool ball on a pool table, the
momentum of the first ball is
transferred to the second ball as
it hits.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
The momentum of this truck is
transferred to this car.
http://www.physicsclassroom.com/mmedia/momentum/trece.html
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
• The Physics Classroom
• Physics Superlink Page
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Let’s Review
-1-
Which of Newton’s 3 Laws
does this illustrate?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Answer
Newton’s First Law of Motion.
“An object in motion tends to stay in
motion until acted on by an
unbalanced force.”
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Let’s Review
-2-
Which of Newton’s Laws are illustrated
in this Crash Test Video?
http://www.hwysafety.org/vehicle_ratings/ratings.htm
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Answer
• Newton’s First Law
• Newton’s Third Law
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Pre-AP Extensions for Chapter 4
• Newton’s Second Law uses the formula
Force = Mass x Acceleration
F = ma
• The units used for Newton’s Second
Law are N = kg x m/s2
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Work the following problems in your
notes about Newton’s Second Law
1. How much force is required to
accelerate a 1000 kg car at 2 m/s2?
2. A force of 10 Newtons acts on a box
which has a mass of 2 kg. What will
be the acceleration of the box?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Forces in Motion
Pre-AP Extensions for Chapter 4
Answers
1. F = ma
F = 1000kg x 2 m/s2
F = 2000N
© Fall 2005, Pflugerville ISD, 7th Grade
2. a = F/m
a = 10N / 2kg
a = 5 m/s2
Unit 1
Work and Machines
What Do You Think?
How can a machine
make work easier?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
• Work occurs when a force causes
an object to move in the direction
of the force.
• A machine is defined as something
that makes work easier.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
There are 6 types of simple
machines that help make
work easier.
1. Lever
2. Inclined Plane
3. Wedge
© Fall 2005, Pflugerville ISD, 7th Grade
4. Screw
5. Pulley
6. Wheel and Axle
Unit 1
Work and Machines
Vocabulary
1. Input force - the amount of force you
must put into the machine.
2. Output force - the amount of force you
get out of a machine.
3. Fulcrum - the fixed point that acts as a
pivot.
4. Load - same as the output force. It is
usually what you are trying to move.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Lever
A lever is a simple machine that
consists of a bar that pivots at a
fixed point, called a fulcrum.
There are 3 classes of levers.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
1st Class Lever
- The fulcrum is between the input force and the
load.
- These levers are used to increase force or
increase distance.
- Examples include a seesaw, scissors, and
pliers.
Where would the fulcrum and the load be in a
seesaw?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
1st Class Lever
http://www.enchantedlearning.com/physics/machines/Levers.shtml
© Fall 2005, Pflugerville ISD, 7th Grade
Item
Number
of Class 1
Levers
Used
see-saw
a single
class 1
lever
hammer's
claws
a single
class 1
lever
scissors
2 class 1
levers
pliers
2 class 1
levers
Unit 1
Work and Machines
2nd Class Levers
- The load is between the fulcrum and the
input force.
- They do not change the direction of the input
force, but they do allow you to apply less
force than the force exerted by the load.
- Examples include a wheelbarrow and a
nutcracker.
Where is the fulcrum, input force and load on
a wheelbarrow?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
2nd Class Lever
http://www.enchantedlearning.com/physics/machines/Levers.shtml
© Fall 2005, Pflugerville ISD, 7th Grade
Item
Number of
Class 2
Levers Used
stapler
a single class
2 lever
bottle opener
a single class
2 lever
wheelbarrow
a single class
2 lever
nail clippers
Two class 2
levers
nut cracker
Two class 2
levers
Unit 1
Work and Machines
3rd Class Levers
- The input force is between the fulcrum and
the load.
- They increase the distance through which
the output force is exerted.
- Examples of these are baseball bats, your
bent arm, and fishing rods.
Where is the input force, output force, and
fulcrum when using a baseball bat?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
3rd Class Levers
Item
Number of
Class 3
Levers
Used
fishing rod
a single class
3 lever
tweezers
Two class 3
levers
tongs
Two class 3
levers
http://www.enchantedlearning.com/physics/machines/Levers.shtml
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Inclined Planes
- An inclined plane is a simple
machine that is a straight, slanted
surface.
- Inclined planes use a longer
distance to exert a smaller force.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Inclined Planes
- An example is a ramp. A smaller
input force is required to move a
piano along an inclined plane
than is needed to lift a piano into
a truck.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Wedge
- A wedge is a double inclined
plane that moves.
- A wedge applies an output force
that is greater than your input
force, but you apply the input
force over a greater distance.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Wedge
- Examples include doorstops,
ax heads, and knives.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Screws
- A screw is an inclined plane
wrapped around a cylinder.
- You apply a small input force
over a large distance, while the
screw exerts a large output
force over a small distance.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Screws
Examples include a screw, jar
lid, soda bottle caps.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Click below to see about
Inclined Planes, Wedges, and Screws
www.unitedstreaming.com
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Pulleys
A pulley is a machine that
consists of a grooved wheel
that holds a rope or a cable.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Pulleys
- A load is attached to one end of the
rope, and an input force is applied to
the other end.
- Examples include flagpoles,
sailboats, blinds, and curtain rods.
- There are two types of pulleys- fixed
and moveable.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Fixed Pulleys
- A fixed pulley has been
attached to a stationary, or
fixed, object.
- Fixed pulleys change the
direction of the force, but they
do not increase force.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Fixed pulleys
You can use fixed
pulleys to pull
down on a rope to
lift up the object.
http://the-office.com/summerlift/pulleybasics.htm
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Moveable Pulleys
- Moveable pulleys increases the
force without changing the
direction of the force.
- The input force must be exerted
over a greater distance than load is
moved.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Moveable Pulleys
The moveable
pulley is attached
to the object
being moved.
http://the-office.com/summerlift/pulleybasics.htm
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Wheel and Axle
- A wheel and axle is a simple
machine consisting of two
circular objects of different
sizes.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Wheel and Axle
- The wheel is the bigger
circle, while the axle is the
smaller of the two.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Wheel and Axle
- Because the axle is smaller
than the wheel, it rotates
through a smaller distance.
This makes the output force
larger than the input force.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Examples of
wheel and
axles are
doorknobs,
wrenches, and
steering
wheels.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
• Most machines that we use
are compound machines.
• Compound machines are
made of two or more simple
machines.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Click below to see simple and compound
machines in action!
www.unitedstreaming.com
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Click below to play a simple machine
game. You must click on the green
“start” button to begin.
Simple Machine Game
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Websites to Visit
•
•
•
•
The Inventor’s Toolbox
Simple Machines Webquest
Simple Machine Basics
Educational Simple Machine Game
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Let’s Review
-1-
Identify the simple
machines that make up
nail clippers.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Answer
• The sharpened edges of nail
clippers are wedges, and the
arm that activates the clipper is
a second class lever.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Pre-AP Extension for Chapter 5
• Scientists have a calculation that is used to
measure how much easier the machine
makes work for us. This is called
Mechanical Advantage.
• The Mechanical Advantage of most simple
machines use the same formula. They use
the words effort force and output
(resistance) force.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
• Effort Force is the force you
put into the machine.
• Resistance Force is the force
exerted by the machine.
Mechanical Adv. = Resistance Force
Effort Force
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Pre-AP Extension for Chapter 5
Try this…
Mr. Kubasta is trying to shove a box full of his
ungraded papers in the back of his car and has to
use a ramp. The ramp length is 2.0 meters long,
and his ungraded papers have a weight of 150
Newtons. The height from the ground to his car is
0.50 meters, and he shoves with a force of 50
Newtons. What is the mechanical advantage of the
ramp he is using?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Pre-AP Extension for Chapter 5
Answer…
• Mechanical Advantage = Resistance Force
Effort Force
• MA = 150 N = 3
50N
• The ramp has a MA of 3, meaning that it is 3
times “easier” to lift the box using the ramp.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Pre-AP Extension for Chapter 5
• There are NO units for Mechanical Advantage
because the Newton’s for each amount of force
cancel each other out.
• The greater the mechanical advantage, the better the
machine.
• The work that you put into a machine is equal to the
work that you get out of the machine.
• By changing the distance you put that work in for,
you can alter the amount of force required to do the
same amount of work.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1
Work and Machines
Websites to Visit
Mechanical Advantage Facts
Mechanical Advantage of a Bicycle
Mechanical Advantage of Pulleys
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 1