1. Gravity and Kinetic Energy Teaching Slides, 2.2
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Gravity and Kinetic Energy Course, 2.2: How Heavy?

2. Focus question
G&KE FQ 2.2
What is gravity like on other planets compared to Earth?
Gravity and Kinetic Energy Course, 2.2: How Heavy?
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3. Gravity scenarios Notebook sheet 8, Response Sheet—Investigation 2
Discuss the two scenarios in your group and record your responses.
Gravity and Kinetic Energy Course, 2.2: How Heavy?
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4. Discuss first scenario
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5. Discuss second scenario
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6. Discuss second scenario
Gravity is one of the basic forces of the universe.
The force of gravity pulls objects together.
You and everything around you is being pulled toward the center of the Earth because it is so massive.
Let’s think about how the force of gravity on Earth compares with other planets.
Gravity and Kinetic Energy Course, 2.2: How Heavy?
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7. Discuss Moon gravity Is there gravity on the Moon? How do you know?
Is the force of gravity on the Moon the same as the force of gravity here on Earth?
Why isn’t the force of gravity on the Moon the same?
Gravity and Kinetic Energy Course, 2.2: How Heavy?
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8. Overview the data Notebook sheet 9, Weight in Various Locations
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9. Overview the data Celestial body: the object being studied
Image and diameter: comparative size of objects
Object mass: mass of object as compared to Earth
Person mass: mass of person measured in kilograms
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10. Overview the data
Person weight: the weight of the person on each object
Gravitational force: 1 represents acceleration of gravity on Earth (9.8m/s2); less than 1 represents a smaller acceleration of gravity.
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11. Overview the data
For example, on Earth the acceleration of gravity is 1 g, that is 1 ✕ 9.8 m/s2.
On Mars, it is 0.38 g, that is 0.38 ✕ 9.8 m/s2.
Gravity and Kinetic Energy Course, 2.2: How Heavy?
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12. Analyze data Notebook sheet 10, Gravity Questions
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13. Analyze data Does the mass of the human change?
Does the weight of the human change?
What does the difference in force depend on?
On which celestial body could you jump highest?
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14. Analyze data
The more massive the object, the ________ the force of gravity.
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15. Analyze data
In general, the bigger the mass, the larger the force is. That force is the gravitational force.
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16. Return to definition of gravity
Turn to your definition of gravity in your notebook. (FQ 1.3) Add additional details to your definition, including how the mass of an object affects it gravitational force.
Gravity and Kinetic Energy Course, 2.2: How Heavy?
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17. Discuss weight on other planets
An object’s weight is related to the gravitational forces acting on it. The person’s 441 N of weight is at 1 g, which is the gravitational force on Earth.
Gravity and Kinetic Energy Course, 2.2: How Heavy?
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18. Discuss weight on other planets
Look at the data table to see what patterns you can identify if you compare the weight of the person on different objects and the gravitational force on each planet.
Gravity and Kinetic Energy Course, 2.2: How Heavy?
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19. Discuss weight on other planets
Using the patterns you identified, how would you calculate a person’s weight on these various celestial bodies?
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20. Earth weight x gravity in Earth g’s
Write the following equation in the empty space below the header in row 6:
Earth weight x gravity in Earth g’s
Gravity and Kinetic Energy Course, 2.2: How Heavy?

21. What would be his weight on Earth?
An average male professional basketball player has a mass of about 100 kg.
What would be his weight on Earth?
How would you find his weight on Mars?
Fill out the second to last row.
Gravity and Kinetic Energy Course, 2.2: How Heavy?

22. Discuss height of jumps
How would you calculate your jump height on these various objects to fill in the last row on the table?
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23. Measure jump heights Jump 3 times to see how high you can get.
Record your best Earth jump in cm on the last line of notebook sheet 9.
Calculate your jump height for the Moon and each planet.
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24. Discuss jumps, force, and mass
On which celestial body could you jump highest?
Why is that?
Why does the Moon have the smallest gravitational force?
On which object would your jump be the lowest?
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25. Discuss jumps, force, and mass
Why is that?
Why does Jupiter have the largest gravitational force?
Work together in your team to come up with a model, using diagrams and text, to explain the results on the Moon and Jupiter.
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26. Exit Ticket
In one sentence, relate the size of a planet to gravity, and to how high you could jump on that planet.
Gravity and Kinetic Energy Course, 2.2: How Heavy?

27. Review other planetary data
Turn to “Acceleration of Gravity on Different Celestial Objects” on page 69 in FOSS Science Resources.
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28. Review other planetary data
Why do you think that Mercury and Mars have the same gravitational acceleration, but different masses? What other information could you consider?
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29. Review other planetary data
Work on the last two questions before we discuss them.
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30. Review other planetary data
Why do you think that Uranus is more massive than Earth, but has less gravitational acceleration?
Why do you think that Saturn is more massive than Neptune, but has less gravitational acceleration?
Gravity and Kinetic Energy Course, 2.2: How Heavy?
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31. Review other planetary data
The gravitational force between objects is related to the distance from their center of mass.
This means that the farther you are from the center of an object, in this case the larger the planet’s diameter, the weaker its gravitational force will be.
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32. Review other planetary data
As you increase the distance between objects (their centers of mass), their gravitational force decreases.
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33. Revisit Newton’s laws Notebook sheet 11, Newton’s Second Law
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34. Revisit Newton’s laws
Newton’s second law: The acceleration (a) of an object is directly proportional to the force on the object (F) and inversely proportional to its mass (m).
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35. Revisit Newton’s laws
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36. Reflect on class experiences
The more massive an object is, the ________ force is needed to accelerate it a given amount.
Fill in the blank and talk in your group what evidence you have that the answer is correct.
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37. Practice with other examples
The more people (greater mass) you load into a car, the ________ it will accelerate with the same force applied by the engine.
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38. Practice with other examples
In the falling-ball video, balls of different masses fell with the same acceleration. That’s because the heavier ball had ________ acceleration due to its greater mass, but it also had ________ acceleration due to the greater force of gravity on the more massive object. The acceleration ended up being unchanged, compared with the lighter ball.
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39. Practice with other examples
How much does a dog of 10 kg mass weigh in newtons? (HINT: The weight is a force, and if the dog were falling, its acceleration would be g.)
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40. Practice with other examples
On Mars, which has 0.38 the gravity of Earth, the acceleration of a dropped ball will be ________ m/s2 and the weight of a 50 kg basketball player would be ________ N.
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41. Answer the focus question
What is gravity like on other planets compared to Earth?
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42. Homework Notebook sheet 12, Investigation 2 Practice Questions
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43. FOSS Science Resources
Read “Gravity in Space” on page 31.
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44. Reading comprehension strategy
Choose one of the images and discuss these questions with a partner.
Why does this illustration interest you?
What do you know about it?
What does it make you wonder about?
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45. Reading comprehension strategy
Record important information as you read.
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