Download Gravity.q (Page 1) - Distribution Access

TEACHER’S GUIDE
Follow-up Discussion
Research indicates that students will retain their previous misconceptions about a topic, in preference to new information, until they
actively recognize and correct their own errors. Therefore, it is important to have your students re-examine the facts/beliefs they put on
their “Everything We Think We Know About…” list. It might also be
helpful to review the list by marking each entry with a “+” or “-” to
show which facts were correct and which were incorrect.
Discussions that ensue from thought-provoking questions provide a
good way to assess the overall depth of student understanding. The
following are some suggested discussion questions.
1. Discuss what would happen to objects on Earth if gravity did not
exist.
2. Ask students to explain what would happen if an elephant and a
peanut were dropped from the same height.
3. Discuss what forces are acting on a kite that’s flying in the air.
TEACHER’S GUIDE
TEACHER’S GUIDE
• www.explorescience.com/freefall.htm
This interactive module from Explore Science allows students to learn
why a feather and a hammer drop at different rates on the Earth, but
identical rates on the moon.
• www.observe.ivv.nasa.gov/nasa/exhibits/toys_space/
factsheet_2.html
This Microgravity page from the NASA Toys in Space Web site explains
how the force of gravity is really felt while astronauts orbit the Earth.
Suggested Print Resources
• Gilbert, Harry. Gravity, the Glue of the Universe: History and
Activities. Teacher Ideas Press, Englewood, CO; 1997.
Gravity
• MacLachlan, James. Galileo Galilei: First Physicist. Oxford University
Press, New York, NY; 1997.
Grades 5–8
• VanCleave, Janice. Gravity. John Wiley & Sons, Inc., New York, NY;
1993.
S
tudents in grade 5–8 classrooms possess a wide range of
background knowledge. Student response to this video
program is sure to be varied, so the teachers at these grades
need all the help they can get! This guide has been designed
to help the 5–8 science teacher by providing a brief synopsis of the program, previewing and follow-up questions,
activities, vocabulary and additional resources.
Before Viewing: Extensive research tells how important
it is for the teacher to discover what the students know —
or think they know — about a topic, before actually starting a new unit.Therefore, after prompting discussion with
the pre-viewing questions, lead your class to create a
“Everything We Think We Know About…” list.You may also
wish to preview key vocabulary words, and have students
raise additional questions they hope will be answered.
Follow-up Activities
• Using a collection of assorted balls, paper, pens and pencils, rocks,
feathers and balloons filled with air and water, have students
examine Galileo’s theory that objects of different mass fall at the
same rate.Ask students to weigh each object before dropping it from
a specific height and timing its fall. Make sure students identify
objects that are affected by air resistance and ask them to draw conclusions about shape and surface area.
• Have students generate a running list of inventions, sports activities,
or other human endeavors that depend on gravity for success.
• Ask students to describe the use of a special antigravity device in a
creative writing activity.
Internet Resources
Periodically, Internet Resources are updated on our Web site at
www.libraryvideo.com
• www.exploratorium.edu/ronh/weight/
This Science Exploratorium site gives students an opportunity to
find out what they would weigh on other planets and explains the
relationship between mass and weight as well as gravity, mass and
distance.
• members.tripod.com/rudytje/gravitatie/gravitatie.html
This page is an interactive gravity modeler that shows how planets
fall into orbits due to the force of gravity, and illustrates the relationship between mass and distance.
(Continued)
5
TEACHER’S GUIDE CONSULTANT
Conrad M. Follmer
25 years as a K–5 Science & Math Coordinator for a Pennsylvania public
school system, currently an independent consultant to elementary schools.
TITLES
• ATOMS & MOLECULES
• CHANGES IN PROPERTIES
OF MATTER
• CHARACTERISTICS OF WAVES
• ELECTRICITY
• ELEMENTS, COMPOUNDS
& MIXTURES
• FLIGHT
• FORCES
Teacher’s Guides Included
and Available Online at:
• FRICTION
• GRAVITY
• LIGHT
• MAGNETISM
• MOTION & BALANCE
• THE PERIODIC TABLE
• PROPERTIES OF MATTER
• SIMPLE MACHINES
• SOUND
800-843-3620
S
R
CHLESSINGE
MEDIA
A DIVISION OF LIBRARY VIDEO COMPANY®
Copyright 2000 by Schlessinger Media, a division of Library Video Company
P.O. Box 580, Wynnewood, PA 19096 • 800-843-3620
Executive Producers: Andrew Schlessinger & Tracy Mitchell
Programs produced and directed by First Light Pictures, Inc.
All rights reserved
TM
After Viewing: Have your students share video excerpts
that fascinated or surprised them, then challenge your students to prove or disprove the accuracy of the facts they
put on their “Everything We Think We Know About…” list.
Discuss what else they learned and use the follow-up questions and activities to inspire further discussion. Encourage
students to research the topic further with the Internet and
reading resources provided.
Program Summary
Vocabulary
Focus Questions
There are many forces at work shaping our world by pushing or pulling
on objects and causing changes in their motion.A force that we couldn’t
live without is the fundamental force of attraction between all objects,
better known as gravity. Sir Isaac Newton, a 17th-century physicist, theorized that the force that pulls an apple to the ground is the same force
that keeps the moon in orbit around the Earth. In 1687, he published his
theory and named it the Law of Universal Gravitation. His theory states
that all objects have gravity regardless of their size, and that an object’s
gravitational force depends on two factors: mass and distance. Mass is the
amount of matter in an object. According to Newton, the greater the
object’s mass, the greater the gravitational pull. However, as distance from
the object increases, the gravitational pull decreases.
Although everything exerts a gravitational pull on everything else, the mass
of the Earth is so great that we do not usually notice the gravity of other
objects.The weight of an object is actually a measurement of the pull of
gravity on the mass of that object. Since the moon has one-sixth the mass of
Earth, its gravity is only one-sixth as strong.That means if you weigh 120
pounds on Earth, you would weigh only 20 pounds on the moon!
Galileo Galilei was an Italian scientist who studied gravity before Newton
was born. In Galileo’s day, most scientists believed that how fast objects
fell was based on how heavy they were and how much mass they contained. Galileo proved that all objects fall to the Earth at the same rate,
regardless of their mass. But if that’s true, why does a bowling ball hit the
ground faster than a feather? This is due to the opposing force of air resistance. If there were no air resistance, all objects would fall to Earth at
exactly the same rate. This is demonstrated in an investigation with a
vacuum pump, a penny and a feather.
When objects are dropped, the force of gravity pulls them to the Earth
and accelerates their fall. Acceleration is any change in motion of an
object. As objects fall their speed increases due to gravity. However, air
resistance stops the acceleration at a given point. As a result, a falling
object will eventually reach a point of terminal velocity and then fall at
that constant speed. Scientists are able to control rocket ships and satellites by balancing their motion with the force of gravity.When a balance
is achieved these objects will orbit the Earth.The enormous gravity of the
sun balanced by the motion of the planets is what keeps the planets of
our solar system in orbit.
The faster you are moving against gravity, the stronger you feel its pull.
This is why astronauts flying through Earth’s atmosphere during a rocket
launch experience something called “g-force” that can make them feel
like they weigh six times heavier than normal! Riding a roller coaster
gives us both the thrill of falling when we feel almost weightless going
downward, and the strange sensation of increased “g-force” as we oppose
gravity going up hills.
The following words are included for teacher reference or for use with
students. They are listed in the order in which they appear in the video.
force — A push or a pull on an object that causes a change in motion.
gravity — The fundamental force of attraction between all objects.The
more mass an object has, the greater the force of its gravity.
Sir Isaac Newton — (1642–1727) The English physicist and mathematician who studied gravitational forces and motion, and is considered the
founder of physical science. Newton formulated the theory of gravity.
The Law of Universal Gravitation — The theory published by Newton
in 1687 that states that all objects, regardless of their size, have a force of
attraction called gravity that is dependent upon both mass and distance.
mass — The amount of matter that is contained in an object.The more
mass an object has, the greater its weight.
weight — A measurement of the force of gravity pulling down on an
object.
Galileo Galilei — (1564–1642) The Italian scientist who proved that
objects fall to Earth at the same rate, regardless of their mass.
air resistance — The force due to air particles that opposes gravity and
slows down motion of objects.
acceleration — Any change in an object’s direction or rate of speed.
terminal velocity — A steady speed achieved by an object falling freely.
Terminal velocity is reached when the force of gravity pulling an object
towards Earth is exactly opposed by the force of air resistance.The terminal velocity of a parachutist is around 240 km per hour.
orbit — The continual path of an object like a planet, satellite or rocket
ship around an object with larger mass.
1.
2.
3.
4.
2
3
Pre-viewing Discussion
Before students generate their list of “Everything We Think We Know
About…” for this topic, stimulate and focus their thinking by raising these
questions so that their list will better reflect the key ideas in this show:
1. What is the force of gravity?
2. How is gravity vital to our existence?
After the class has completed their “Everything We Think We Know
About…” list, ask them what other questions they have that they hope
will be answered during this program. Have students listen closely to
learn if everything on their class list is accurate and to hear if any of their
own questions are answered.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
What are forces?
What is the force that pulls things to Earth?
How is gravity defined?
What contribution did Sir Isaac Newton make to our understanding of gravity?
What is Newton’s Law of Universal Gravitation?
What kinds of objects exert a gravitational pull?
What are the factors that affect the gravitational pull of objects?
If everything with mass has gravity, why aren’t we noticeably
pulled by the gravity of a mountain or building? Explain.
What is the difference between mass and weight?
Under what conditions can we feel “weightless”?
Why does weight vary but not mass?
Who was Galileo Galilei?
What was Galileo’s contribution to our understanding of gravity?
How did he prove his theory?
If you dropped a brick, a tennis ball and a maple leaf from a
second floor window on Earth, in what order would they land?
Explain.
If you dropped a brick, a tennis ball and a maple leaf from a
second floor window on the moon, in what order would they
land?
What is the relationship between air resistance and gravity?
What are some examples of activities or inventions that manipulate air resistance to slow things down or speed them up?
What is acceleration?
Why do objects accelerate as they fall to the ground?
What is terminal velocity?
What is free fall?
What forces need to be balanced in order for a satellite to remain
in orbit around the Earth?
How do the planets and moons in our solar system remain in orbit
around the sun?
What are some effects of gravity upon astronauts during a shuttle
launch?
What are some effects of gravity felt by people riding a roller
coaster?
4