Motion of Objects in Space S6E1e Explain that gravity is the force that governs the motion in the solar system.

Write your Thoughts Why do planets revolve (go around) the sun? Why does the moon revolve around the Earth? What forces make it do this? No answer is wrong! Just tell me what you think!

Vocabulary: Record definitions Gravity—a force that attracts or pulls masses towards each other Gravitational Pull—the force of gravity causing an object to move towards it. Weightlessness—a state lacking apparent gravitational pull Free Fall—the condition of unrestrained motion in a gravitational field

1. Gravity Gravity depends on two things: The mass of the two objects. The distance between them. The more mass two objects have, the stronger the pull of gravity.

Mass Definition Reminder: a measure of how much matter an object is made of

The more mass two objects have, the stronger the pull of gravity.

Gravity The farther apart they are, the weaker the pull of gravity. Gravity depends on two things: The mass of the two objects. The distance between them. The farther apart they are, the weaker the pull of gravity.

The farther apart they are, the weaker the pull of gravity. http://www.freezeray.com/flashFiles/gravity.htm The farther apart they are, the weaker the pull of gravity.

Show me what you know: Answer number 4 and 5 on your notes

Check your work: 4. b 5. a If you missed either one, go back and review this presentation. If you still don’t understand, ask Ms. Stone for help.

Inertia Inertia is the tendency of a moving object to continue in a straight line or a stationary object to remain in place.

Force of gravity Inertia inertia

Show me what you know! Answer #8

Check your work: 8. b

Orbits! Orbit: The path of an object as it revolves around another object in space. Question: What two forces work together to create an orbit? Gravity & inertia!

Shape of Orbits Think: What shape was the orbit you drew in your model of the solar system?

The shape of orbits in space… An ellipse!... Draw it!

STOP HERE AND GO TO NEXT STEP!!!!!!!

Class Competition! 1. What force keeps Earth in orbit around the sun? A pull by one object that is in contact with another object A push by one object that is in contact with another object Mass Gravity

2. What affects the force of gravity between two objects? The mass of the objects and the distance between them The mass of the objects and inertia The distance between the objects and inertia The mass of the objects, the distance between them, and the inertia

3. In what direction does an object in space tend to move? In a curved path Inward In a straight line Backward

4. How would the force of gravity between Earth and the sun be affected if the mass of Earth were greater than it is? The force of gravity would be greater The force of gravity would be unchanged The force of gravity would be less There would be no force of gravity

5. If the force of gravity between Earth and the sun were greater than Earth’s inertia, what would happen to Earth? Earth would escape into space Earth would fall into the sun Earth would remain in its orbit around the sun Earth would stop moving

6. Of the 8 planets, why does the sun have the least gravitational attraction to Neptune? Because Neptune has poisonous methane gas Because Neptune is the farthest planet from the sun Because Neptune is the smallest planet Because the other planets are between the sun and Neptune

7. An astronaut, Samantha, is in space moving closer to Earth 7. An astronaut, Samantha, is in space moving closer to Earth. How would the gravitational force between the astronaut and Earth change? Gravitational pull on the astronaut would increase Gravitational pull on the astronaut would decrease There would be no change in the gravitational pull between the Earth and the astronaut

8. What is the definition of gravity

9. If the distance between two objects decreased what would happen to the force of gravity? It would increase It would decrease It would stay the same It would stop

10. If the mass of an asteroid orbiting the Sun were decrease, what would happen to the force of gravity between it and the Sun? It would decrease. It would stay the same. It would increase. It would experience an unknown effect.

11. When the same distance apart, which has a weaker force of gravity between them? a. the earth and the moon b. the earth and a man on the moon

12. What would happen to the moon if the force of gravity suddenly disappeared? a) The moon would crash into Earth b) The moon would fly away from Earth c) The moon would continue orbiting Earth d) The moon’s speed around Earth would slow down

13. Draw and Name the shape of objects orbits in space.

Double Points: 14. In each diagram (see image), the mass of the star is the same. Circle the diagram where the force of gravity greatest between the star and the planet shown? 2 2 3 3 1