Gravity What is Gravity?

Pick up a Brain Pop: Observation Chart from the front table. You have five minutes from the time the bell rings to complete it. After you have completed your Bellringer write your homework in your Planner Bellringer

TLW be able to describe what determines the strength of the force of gravity between two objects. Explain what two factors combine to keep the moon & Earth in orbit. Objectives

Gravity Terms Force Gravity Law of universal gravitation Mass Weight Inertia Gravity

Gravity What keeps Earth & the moon in orbit? Why don’t they just fly off into space? Gravity

Gravity Force: Push or a pull The force that attracts bodies of matter toward each other. Force: Push or a pull The force that holds the moon in orbit is different; it acts over long distances between objects that are not in contact. Gravity

Gravity Gravity: A force that attracts all objects toward each other. Newton’s law of universal gravitation: Every object in the universe attracts every other object. Gravity

The strength of the force of gravity between two objects depends on two factors: The mass of the object The distance between them Gravity

Gravity Mass: The amount of (stuff) matter in an object Weight: The force exerted on an object’s mass by gravity. Gravity Because the Earth is so massive, it exerts a much greater force on you than this book does. Earth exerts a gravitational force on the moon, large enough to keep the moon in orbit. The moon also exerts a gravitational force on Earth. (Tides) Mass does not change; however, an object’s weight can change depending on its location. For example, on the moon you wuld lweigh about 1/6 of your weight on Earth. This is because the moon is much less massive than Earth, so the pull of the moon’s gravity on you would be far less than that of Earth’s gravity.

Objects that are far apart exert less gravitational force on each other than objects that are close together. Mass & Distance The force of gravity decreases rapidly as distance increases.

objects toward one another Force of Gravity Mass & Distance Gravity attracts all objects toward one another The force of gravity decreases rapidly as distance increases. If mass increases, force also increases

If distance increases, force decreases. Force of Gravity Mass & Distance If distance increases, force decreases. The strength of gravity is affected by the distance between two objects as well as their masses. The force of gravity decreases rapidly as distance increases.

Inertia & Orbital Motion If the sun & Earth are constantly pulling on one another because of gravity, why doesn’t Earth fall into the Sun? Inertia & Orbital Motion

Inertia & Orbital Motion Inertia: The tendency of an object to resist a change in motion. Inertia & Orbital Motion You feel the effects of inertia every day. Riding in a car & it stops suddenly, you keep moving forward. The more mass an object has, the greater its inertia. An object with greater inertia is more difficult to stop.

Inertia & Orbital Motion Newton concluded that two factors: Inertia Gravity Combine to keep Earth in orbit around the sun & the moon in orbit around the Earth. Inertia & Orbital Motion Earth’s gravity keeps pulling the moon toward it, preventing the moon from moving in a straight line. At the same time, the moon keeps moving ahead because of its inertia. In the same way, Earth revolves around the sun because the sun’s gravity pulls on it while the Earth’s inertia keep it moving ahead.

TLW be able to describe what determines the strength of the force of gravity between two objects. Explain what two factors combine to keep the moon & Earth in orbit. Conclusion

Activity Falling to Earth Falling Race Paper Race Trick Paper Parachute Tests Activity Take a look at gravity using objects of different mass to tests the affects of gravity.