Download Gravity Workbook

Name _____________________________________________________________
Gravity
Workbook
1
This Workbook covers the following Utah State Core
Standards:
STANDARD III: Students will understand the
relationship and attributes of objects in the Solar
System.
Objective 3: Describe the forces that keep objects in
orbit in the Solar System.
a. Describe the forces holding Earth in orbit around
the Sun, and the Moon in orbit around Earth.
b. Relate a celestial object’s mass to its gravitational
force on other objects.
c. Identify the role gravity plays in the structure of
the Solar System.
2
Quicker
(activity from Astronomy for Every Kid by Janice Van Cleave)
Materials
 Long stick
 Short stick
 Modeling clay
Procedure
1. Place a walnut-sized ball of clay on the end of the long
stick and one on the end of the short stick.
2. Hold the long stick and short stick up and down, sideby-side, with the edge without the clay ball on the ground.
3. Release both at the same time.
1. Explain what happened when you dropped the sticks.
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
3
2. From your notes, you know that planets nearer the Sun revolve faster than planets
away from the Sun. Explain how activity demonstrates that concept.
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
Staying Up While Falling Down
Materials
 Plastic golf ball
 Straw
 Different size washers
Safety Concerns: Moving plastic golf
ball. Discuss safe procedures for
twirling ball and pulling washers.
Procedure
1. Thread the string through the
straw. DO NOT tie a washer to the
other end of the string. Your set up
should look like the diagram below
(except no washer).
4
2. Hold the straw and swing the ball in a circle so that it “orbits” the straw. (Be sure to
keep moving your hand at a constant speed.) Record below what you see happen.
__________________________________________________________________
__________________________________________________________________
3. Tie a small washer to the end of the string. Hold the straw and swing the ball in a
circle so that it “orbits” the straw. (Be sure to keep moving your hand at a constant
speed.) Record below what you see happen.
__________________________________________________________________
__________________________________________________________________
4. Tie a medium sized washer to the end of the string. Hold the straw and swing the
ball in a circle so that it “orbits” the straw. (Be sure to keep moving your hand at a
constant speed.) Record below what you see happen.
__________________________________________________________________
__________________________________________________________________
5. Tie a large washer to the end of the string. Hold the straw and swing the ball in a
circle so that it “orbits” the straw. (Be sure to keep moving your hand at a constant
speed.) Record below what you see happen.
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
We have your rovers. If you want them back, send 20 billion in Martian
money. No funny business or you will never see them again.
- Seen on a hall wall at NASA's Jet Propulsion Labs
5
6. Tie two or more large washers the end of the string. Hold the straw and swing the
ball in a circle so that it “orbits” the straw. (Be sure to keep moving your hand at a
constant speed.) Record below what you see happen.
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
7. Explain how this experiment demonstrates planets revolving around the Sun.
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
Orbital Period: Time of Revolution
(an activity from Janice Van Cleave’s A+ Projects in Astronomy)
Question
How does distance effect the orbital period of an orbiting planet?
Materials




Metal washer
6-foot string
Ruler
Timer
6
Safety Concerns: Flying washer.
Student must make sure washer is
properly tied to string and space is left
between students swinging the washer.
Procedure
1. Tie a washer to the cord.
2. On the cord, measure 18” from the washer and time a knot in the cord.
3. Measure 18” from the knot and tie a second knot in the cord. Repeat this process a
third time, making a third knot.
4. Hold the cord at the first knot (18”) from the washer and swing your arm so that the
washer spins above your head.
5. Find the slowest speed that will keep the washer “in orbit.”
6. Have a partner count the revolutions. The partner will say “Start” and count the
number of revolutions in 10 seconds.
7. Stop when your partner says, “stop.”
8. Calculate the orbital period, T (time per revolution) of the washer by dividing the
time by the number of revolutions. For example, if your partner counted five
revolutions in 10 seconds the orbital period would be:
 T = orbital period = time  number of revolutions
 = 10 seconds ÷ 5 revolutions
 = 2 seconds per revolution (2 seconds/revolution)
This is read as 2 seconds per revolution and means that it took 2 seconds for the
washer to travel 1 revolution.
7
9. Repeat steps 6 thru 8 for a total of five trial measurements.
10. Repeat steps 6 thru 8 for the two other distances (36” at the second knot and 54”
at the third knot.)
11. Record your data in the Orbital Period by Orbit Distance table. Make sure you
figure the average of the five trials. For example:
 Trial 1 – 2 seconds/revolution; Trial 2 – 2.7 seconds/revolution; Trial 3 – 1.9
seconds/revolution; Trial 4 – 2.2 seconds/revolution; Trial 5 – 1.4
seconds/revolution.
 = 2 + 2.7 + 1.9 + 2.2 + 1.4
 = 10.2 (total five trials)
 = 10.2 ÷ 5 (number of trials)
 = 2.04 seconds/revolution (average of the five trials)
Question
How does distance effect the orbital period of an orbiting planet?
1. Complete the table below.
Orbital Period by Orbital Distance
Orbital Distance
(Inches)
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Average
18”
36”
54”
8
2. Using the data in your table and graph, explain how the length of the string effects
the orbital period (revolutions/second) of an orbiting planet.
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
Free Falling
(an activity from the Texas Space Grant Consortium)
Four hundred years ago--or so the story goes--Galileo Galilei started dropping things
off the Leaning Tower of Pisa: Cannon balls, musket balls, gold, silver and wood. He
might have expected the heavier objects to fall faster. Not so. They all hit the ground
at the same time, and so he made a big discovery: gravity accelerates all objects at the
same rate, regardless of their mass or composition.
Was Galileo correct?
Materials




Triple-Beam Balance
Four Kodak Film Canisters
Washers
Marker
Safety Concerns: None.
Procedure
1. Label the film canisters 1-4. Place one washer in canister one, two in canister two,
three in canister three and four in canister four.
2. Using the triple-beam balance, determine the mass of each canister. Record it on
your table.
9
3. Select two canisters and hold them at arm’s length, facing the same way.
4. Release both canisters and observe if they both hit the ground at the same or
different time. Repeat the process three times.
5. Repeat for every combination of canisters.
Data Table
Mass of Canisters
Canister #
Mass (grams)
1
2
3
4
Observations
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
10
1. Are your results the same for each trial? Explain.
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
_________________________________________________________________
2. Does your observation verify Galileo’s hypothesis? Explain.
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
_________________________________________________________________
3. Would an elephant fall faster than a mouse? Explain.
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
_________________________________________________________________
11
Gravity Exploration
Part A: How much would you weigh on other bodies?
The more mass an object has, the more gravity it has. Objects that have more mass than Earth
would have more gravity than Earth. A person would weigh more on these objects than they do
on Earth.
Write your weight in the “Weight on Earth” column. If you don’t know your weight, use 93
pounds. Figure out how much you would weigh on other bodies.
Location
Your Weight
Gravity
on Earth
Calculated Weight
(round decimals to a
whole number)
Sun
X
27
Mercury
X
.38
Venus
X
.86
Moon
X
.17
Mars
X
.38
Ceres
X
.03
Jupiter
X
2.87
X
.18
X
.13
X
.15
X
.13
X
1.32
Jupiter’s Moon
Io
Jupiter’s Moon
Europa
Jupiter’s Moon
Ganymede
Jupiter’s Moon
Callisto
Saturn
12
Uranus
X
.93
Neptune
X
1.23
Pluto
X
.067
Part B: How far could you jump on other planets and the moon?
Determine how far you can jump on the Earth. To do this, place a piece of tape on the
floor as a starting line. Jump as far as you can off of both feet. Have your partner mark
where you land not where you end up! Measure the distance and record in the table. Do
this five times, and then find the average.
Jump 1
Jump 2
Jump 3
Jump 4
Jump 5
Average
(To find the average, add Jump 1 + Jump 2 + Jump 3 + Jump 4 + Jump 5 and
then divide your total by 5. This is the distance that goes in the average column.)
Location
Average
Gravity
Length (round
Convert to
Length on
decimals to a
Feet (Divide
Earth
whole number)
Length by 12)
Sun
÷
27
Mercury
÷
.38
Venus
÷
.86
Moon
÷
.17
Mars
÷
.38
Ceres
÷
÷
÷
.03
Jupiter
XXXXXXXXXX
2.87
13
Jupiter’s
Moon Io
Jupiter’s
Moon
Europa
Jupiter’s
Moon
Ganymede
Jupiter’s
Moon
Callisto
÷
÷
÷
÷
.18
.13
.15
.13
Saturn
÷
1.32
Uranus
÷
.93
Neptune
÷
1.23
Pluto
÷
.067
Chaos Among the Planets
Kate Ramsayer
From Science News for Kids June 1, 2005.
Once upon a time, many, many years ago, the giant planets in our Solar System took
different paths around the Sun than they follow now.
Jupiter, Saturn, Uranus, and Neptune were once bunched together and closer to the
Sun, says an international team of scientists. Under the influence of gravity, the planets
broke out of their original orbits and began violently rearranging the outer Solar
System.
14
A new theory suggests that the four giant planets,
shown here in their current orbits around the Sun,
were once much closer together.
Nature
It's "a fairy tale of the early Solar System," says Hal Levison. He's a planetary
scientist with the Southwest Research Institute in Boulder, Colo., and was one of the
researchers who developed a computer simulation of the planets' movements.
As the scientists tell it, the tale starts a few million years after the Solar System's
birth. At first, the four giant planets had compact orbits. Neptune, for example, was
only half as far away from the Sun as it now. A slowly circulating band of ice, dust, and
gas lay beyond these planets.
Ice, dust, and gas might not seem like much of a match for huge planets. But the
researchers say that the pull of gravity between the particles and the planets caused
the planets to gradually break out of their tight-knit group. Jupiter moved a bit closer
to the Sun, and the other three planets moved further away.
All was peaceful in the solar kingdom until the orbits of Saturn and Jupiter aligned so
that Saturn took exactly twice as long as its neighbor to go around the Sun. The
increased gravitational tug of the two planets acting together caused an avalanche of
effects.
Saturn's orbit changed shape slightly, which threw off the orbits of Uranus and
Neptune. The orbits of these two planets started looking like squished ovals. At times,
the two planets even crossed paths.
And that's when things got really crazy. Uranus and Neptune started hurtling through
the band of ice, dust, and gas, scattering the debris throughout the Solar System. The
planets themselves ended up in their current orbits.
15
In the meantime, some of the scattered material became trapped around Jupiter, the
scientists suggest. This could account for the presence of objects, known as the Trojan
asteroids, that both lead and trail the planet.
Some of the debris could have been flung closer to our home, slamming into the Moon
and the Solar System's inner planets. This bombardment may have created the huge
craters on the Moon and elsewhere.
No one knows for sure whether all this really happened. But, by using computers to play
complex games of "what if," scientists can get a better sense of what might have
happened to create the Solar System as we know it.
Questions
1. According to the article, these four planets were bunched together and nearer to
the Sun.
a. ___________________________________________________________
b. ___________________________________________________________
c. ___________________________________________________________
d. ___________________________________________________________
2. This force caused the violent rearrangement of our Solar System.
__________________________________________________________________
3. __________________ orbit changed shape slightly, which threw off the orbits of
_________________________________________.
4. This is the group of asteroids that both lead and trail Jupiter.
__________________________________________________________________
5. Debris flung towards the inner planets may have created the huge _____________
on the Moon and elsewhere.
6. Scientists are positive this really happened.
True
False
16