Chapter Seven Section Two Gravity and Motion Chapter Seven Section Two

Gravity Definition: The attractive force between objects (Force: A push or pull) The Law of Gravity (Newton’s Law of Universal Gravitation): Every object in the universe attracts every other object

The force of gravity is measured in newtons (N) The strength of the force between two objects depends on two factors: The masses of the objects The distance between them

Gravity, Mass, and Weight Mass: The amount of matter in an object The greater the mass, the stronger the force of gravity The sun>Earth>moon Earth revolves around the sun The moon revolves around earth

Gravity, Mass, and Weight Weight: The force of gravity on an object Weight can change depending on location Since the moon is smaller than Earth, an object there is 1/6 its weight on Earth. How much would you weigh on the moon?

Gravity, Mass, and Weight The strength of gravity is affected by the distance between the two objects as well as their masses Gravity increases the closer the objects are to each other The farther away the objects are, the weaker the pull becomes

Inertia and Orbital Motion Inertia keeps the Earth from crashing into the sun, and the moon from crashing into Earth Inertia: The tendency of an object to resist motion Newton’s First Law of Motion: An object at rest will stay at rest and an object in motion will stay in motion with constant speed and direction unless acted on by a force. Inertia and gravity combine to keep the Earth in orbit around the sun and the moon in orbit around the earth.

Inertia and Orbital Motion Think of Earth as the ball in a tetherball game. The sun is the pole Gravity is the tether (rope) that attaches the ball to the pole Inertia is the forward motion of the ball after it is hit.