1. Chapter 6 Lesson 3: Gravity and Orbit

2. What is gravity?
Gravity is the force of attraction, or pull between any two objects
Each planet is drawn toward the sun by gravity
Gravity is affected by the total mass, and distance between the two objects
An object’s mass always stays the same
Your weight depends on mass, as well the force of gravity wherever you are located

3. Weight and Gravity Mass on Earth = 100 Weight on Earth = 100lbs
Earth’s gravity =1
Mass on Jupiter = 100
Weight on Jupiter = 236lbs
Jupiter’s gravity = 2.36
Mass on Moon = 100
Weight on Moon = 16.5lbs
Moon’s gravity = .165

4. What keeps objects in orbit?
An orbit is a path an object takes around another
Planets orbit the sun
Moons orbit their planets

5. Inertia Inertia is the tendency of a moving
object to keep moving in a straight line.
All objects have the property of inertia.
Inertia alone would cause Earth to move in a straight line.
Gravity and inertia together make Earth follow its path of orbiting
the sun.
The effect of gravity and inertia make the planets move in a circular
orbit called an ellipse.

6. What causes the tides?
Both the pull of gravity from the moon and sun affect Earth
Moon is closer to Earth than the sun
Sun’s pull of gravity is less than the moon’s pull of gravity
Tide is the rise and fall of the ocean’s surface
Most oceans have two high tides and two low tides

7. As the moon orbits around the earth, its gravity pulls water on the side nearest to it away from the land. This causes low tide
About twice a month, the sun and the moon line up and both pull in the same direction. This causes higher tides and lower tides called “spring tides”
Neap tides are tides with the smallest range which occur between spring tides, caused when the sun and moon pull in different directions

8. Review Questions
Jupiter is about 320 times larger than Earth, but its gravity is only 2.36 times larger than Earth’s gravity. What might cause this difference?
Suppose you have a dog that weighs 50lbs. How much would it weigh on a planet that had 3.45 times Earth’s gravity?
Why dies food float in the space vehicle of the astronauts don’t hold onto it?
Why do stronger tides occur when the sun and moon are lined up?
Why do spring and neap tides occur twice a month?
How is the gravity between two objects affected by their masses?
The rise and fall of the ocean’s surface is the _____________.
How are mass and weight different?
What force keeps earth in its orbit around the sun?
What tide occurs twice a month when the sun and moon pull in different directions?