2 What is gravity?Gravity is the force of attraction, or pull between any two objectsEach planet is drawn toward the sun by gravityGravity is affected by the total mass, and distance between the two objectsAn object’s mass always stays the sameYour 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 =1Mass on Jupiter = 100Weight on Jupiter = 236lbsJupiter’s gravity = 2.36Mass on Moon = 100Weight on Moon = 16.5lbsMoon’s gravity = .165
4 What keeps objects in orbit? An orbit is a path an object takes around anotherPlanets orbit the sunMoons 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 orbitingthe sun.The effect of gravity and inertia make the planets move in a circularorbit called an ellipse.
6 What causes the tides?Both the pull of gravity from the moon and sun affect EarthMoon is closer to Earth than the sunSun’s pull of gravity is less than the moon’s pull of gravityTide is the rise and fall of the ocean’s surfaceMost 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 tideAbout 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 QuestionsJupiter 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?