1. Inertia and Gravity

2. Activity One Marble Lab
Place the marble on the paper in the tray. Invert the plastic cup over the marble.
Move the cup in a rapid circular motion, causing the marble to move around the inside edge of the cup.
While the marble is moving rapidly in the cup, lift the cup straight up off the paper.
Record in your journal what happens to the marble.
Repeat the activity, paying careful attention to the path of the marble takes after lifting the cup.
Explain the marble’s motion.
Draw an explanation of the marble’s motion in your journal; be sure to label the drawing. (Cup, Marble and Path of the marble

3. Marble Lab Questions to discuss
Marble lab after looking at all illustrations.
1. What do all of the illustrations have in common?
2. What kept the marble moving in a circular pattern?
3. Inertia is an object’s resistance to a change in its motion. This means objects at rest will stay at rest, and objects that are moving will continue to move in a straight line unless they are acted on by an unbalance force. How does the concept of inertia apply to this activity?

4. Spinning Sphere lab Activity 2 Watch the teacher demonstration.
Read the slides on Inertia and Gravity.
Answer following questions: Planet Motion
Describe how the planets are kept in motion within their orbit.
Describe the role of inertia plays in keeping the planets within their orbit.
Describe how Newton’s law of the universal gravitational applies to the motion of the planets in our solar system.
Draw diagram in your journal of the Orbit of a planet.

5. Spinning Sphere Questions
1. What does the ball represent in this model?
2. What do the washers represent?
3.What happens when we whirl the model faster?
4. When we whirl the model, what allows the ball to remain in a circular pattern?
5. What would happen if we let go of the ball?

6. More Questions 6. What is a force?
7. Gravity is a pulling force. How is gravity represented in this model?
8. How is the concept of gravity applied to the Sun and planet?
9. What would happen if there was not gravity between the planets and the Sun?

7. Early Greek and Roman observations
Early Greek and Roman astronomers were the first to observe that planets seem to move around in the sky while stars appear to be more stationary in their positions. In fact, the word planet comes from the Greek word planasthai, which means “to wander.”

8. Johannes Kepler
During the 1600s, a German astronomer named Johannes Kepler made careful observations of planets and their movements around the Sun. Kepler discovered that planets travel around the Sun in a particular path called an orbit. One complete orbital path around the Sun is a revolution.

9. Sir Isaac Newton
Later during the same century, Sir Isaac Newton made several discoveries that helped explain Kepler’s observation about the orbits of planets. Newton’s law of universal gravitation states that every object in the universe attracts every other object.

10. Two Important Factors:
How strongly objects pull on each other depends upon two factors:
How much matter the objects have (mass)
How far apart the objects are (distance)

11. Inertia
The Sun has a gravitational pull on planets. Inertia is an objects resistance to any change in its motion. Objects at rest will stay at rest, and objects moving will continue to move in a straight line unless they are acted on by an unbalanced force. Without the gravitational force between the Sun and the planet, the planet would travel off into space in a straight line, (like your marbel did)

12. The Sun gravitational Pulls causes Planets to orbit.
Each planet continues to move forward because of its inertia, but due to the force of gravity, the planet travels in a curved orbit.

13. Select one of the following to write about in your journal
1. Describe how the planets are kept in motion within their orbit.
2. Describe the role inertia plays in keeping planets within their orbit.
3. Describe how Newton’s Law of universal gravitation applies to the motion of the planets in our solar system.

14. Weight in the Solar System
Location in Solar System
Gravity at Surface (When Earth=1)
Weight at Given Location
Sun
27.9
2790
Mercury
0.37
Venus
0.88
Earth
1.00
Earth’s Moon
0.17
Mars
0.38
Jupiter
2.13
Saturn
0.74
Uranus
0.86
Neptune
1.07
* Multiply the number by 100 N

15. Based on the table, at which location in the solar system will the object weigh the most?
Based on the table, at which location will the same object weigh the least?
How does changing the location of the object affect the mass of the object?
How does changing the force of gravity pulling on an object affect its mass?