ID:_______Name: _____________________________________________Date:____________________Class:______
Gravity and Orbits Lab –LAB ACTIVITY SHEET
Learning Objectives- You will be able to:
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Draw motion of planets, Moons and satellites.
Draw diagrams to show how gravity is the force that controls the motion of our solar system.
Identify the variables that affect the strength of the gravity.
Predict how motion would change if gravity was stronger or weaker.
Part 1: Understanding motion
1. Open the Gravity and Orbits simulation.
http://tinyurl.com/PHETorbit
Take a few minutes to PLAY & explore how the Earth, Moon, and the Space Station move. Talk about what you find
with your group.
GROUP DISCUSSION: What controls have you found? What do they do?
2. Compare the motion of the Earth moving around the Sun with the Moon moving around the Earth.
Earth moves around the Sun
Moon moves around the Earth
Your Picture
Your Picture
Your Description
Your Description
a. What are some things you find that are similar about these motions?
b. What are some things you find that are different about these motions?
3.
Based on your observations, how would you define the word “orbit”? Cite evidence!
Part 2: Understanding Gravity For the Sun and Earth system:
4. Draw/LABEL the Sun’s gravitational pull on the Earth
Draw/LABEL the Earth’s gravitational pull on the Sun
5. What do you think the gravity force arrows represent?
6. What do you notice about the size of the gravity force arrows?
7. In what directions do the arrows point?
What do you think this means?
8. Explore the simulation to find out how you can change the force of gravity and observe what happens.
GROUP DISCUSSION: Share what you found with the group.
9. Draw the path,
force vectors AND velocity vectors of the Earth around the sun (in the below diagrams) with
Gravity ON and Gravity OFF.. be sure to LABEL your diagrams!
GRAVITY ON
GRAVITY OFF
10. What direction is the gravitational force of the orbiting object? (Gravity ON)
11.
What direction is the velocity of the orbiting object? (Gravity ON)
12. What direction is the gravitational force of the gravity OFF object?
13.
What direction is the velocity of the gravity OFF object?
14. If you turn gravity off, what happens? Why does this happen? (THINK back to Ch. 9!)
 Variable- A variable is any factor that can be changed or controlled
 Independent Variable – something that is changed by the scientist
 What is tested
 What is manipulated
 Dependent Variable – something that might be affected by the change in the
independent variable
 What is observed
 What is measured
 The data collected during the investigation
15.
Complete the following table. Then, hypothesize AT LEAST 1 more – add them and collect data (feel free to try
more)
Independent
Variable
What Happens? (to earth, to the orbit paths, to the force of
Dependent Variable (look at what
gravity, etc.)
happened…use that the boxed info above
to fill in)
Put sun and
earth closer
together
Move sun and
earth farther
apart
Increase the
mass of the sun
Decrease the
mass of the sun
Click on the
Earth/satellite button.
Increase the speed of
the satellite.
Decrease the
speed of the
satellite
Change the mass of the
satellite only. Will this
change the orbit of the
satellite? Why or why
not?
Move the
satellite closer
to Earth
Move the satellite
farther from Earth
CHALLENGE: Can you create a stable orbit further from the
Earth? How did you do it?
Part 4: comparisons
16. Compare these two cases:
CASE 1
CASE 2
a. What was changed between Case 1 and Case 2? How did it affect gravity?
b. Draw the force of gravity on the Earth in each case; draw on the actual diagrams in 16.
17.
Compare these two cases:
CASE 1
CASE 2
a. What was changed between Case 1 and Case 2? How did it affect gravity?
\
b. Draw the force of gravity on the Earth in each case; draw on the actual diagrams in 17.
Part 5 : Gravity and Motion
1. Fill in the table to help describe what you find out.
How can you….
Explain what you changed
Draw the motion paths
What other changes do you
notice?
...make the Moon
go around the Earth in a
bigger circle?
...make the Earth
take more time to go
around the Sun?
...make the Earth
take less time to go
around the Sun?
18.
CIRCLE your answer: Gravitational force is always attractive / repulsive.
19.
CIRCLE your answer: Gravitational force exists everywhere / only in some places in the universe
20.
CIRCLE your answer: IF a gravitational force exists between two objects, one very massive and one less
massive, then the force on the less massive object will be greater than/ equal to / less than the force on the
more massive object.
21.
CIRCLE your answer: As the distance between masses decreases, force increases / decreases.
22.
How does gravity affect the motion of orbiting objects?
23.
Based on your observations, how would you define the word “gravity”? Cite evidence!
24.
What factors can affect the strength of gravitational force?
25.
Venus is called Earth’s “sister” planet because it is almost the same size (mass & diameter) as Earth. BUT –
Venus is closer to the Sun.
CIRCLE your answer: The Sun has a (stronger / weaker) gravitational pull on Venus than it does on Earth.
a. EXPLAIN:
26.
The earth’s gravity is pulling on you. Are you pulling on the earth? Explain your reasoning.
27.
Gravity is a force of attraction between objects based on their mass and their distance apart. Why aren’t
other objects, like your pencil, being pulled towards you? Explain your reasoning.
28.
In any of the situations did the forces ever point in opposing directions? Explain why or why not:
29.
GROUP DISCUSSION: Why do you think the Earth orbits the sun, not the other way around?
30.
SUMMARIZE what you learned today: