BELLWORK What is gravity Do you think gravity

BELLWORK: What is gravity? Do you think gravity is the same everywhere? Explain. (5 mins. )

GRAVITY AND MO TION

NEXT GENERATION SCIENCE STANDARD MS-PS 2 -4. Construct and present arguments using evidence to support the claim that gravitational interactions are attractive and depend on the masses of interacting objects.

OBJECTIVES Content Objective: Language objective: Students will be able to describe the effect that gravity, including Earth’s gravity has on matter. Students will be able to define gravity, free fall, and orbit.

VOCABULARY: Gravity: is a force of attraction between objects due to their mass. Free fall: when gravity is pulling it down and no other forces are acting on it. Orbit: when an object travels around another object in space

GRAVITY IS AN ATTRACTIVE • FORCE Earth’s gravity pulls everything toward Earth’s center. • It pulls, but it does not push, so it is called an attractive force. • You feel the force due to Earth’s gravity as the heaviness of your body, or your weight. • Weight is a force and it depends on mass. • Greater mass results in greater weight. • Force=mass x gravity, where g is about 9. 8 m/s 2 • Earth’s gravity accelerates all objects in the same way. • Sometimes an object experiences a lot of air resistance and falls slowly to the ground.

This is the part where you laugh…LOL

Is a force of attractio n between objects due to their Gravity is a result of mass, so all matter is affected by gravity. The larger the mass, the stronger the

Gravity

Gravity between two objects increases as the distance between their centers decreases. Gravity between two objects decreases as the distance between their centers increases. Ex. You can’t feel the sun’s gravity because it so far away, but if you were able to stand on the surface of the sun, you would find it impossible to move due to gravity!

WHAT DETERMINES THE FORCE OF GRAVITY? • The law of universal gravitation relates gravitational force, mass, and distance. • It states that all objects attract each other through gravitational force. • The strength of gravity depends on mass and distance.

GRAVITY DEPENDS ON DISTANCE • Objects far apart have weaker attraction than objects close together. • If two objects move closer, the attraction between them increases.

GRAVITY DEPENDS ON MASS • Gravitational force between two objects increases with the mass of each object. • Objects with greater mass have more attraction between them. • Example: a cow has more mass than a cat, so there is more attraction between the Earth and the cow, and the cow weighs more. • This explains why astronauts bounce on the moon because the moon has less mass than Earth, so astronauts weigh less.

HOW DOES GRAVITY KEEP OBJECTS IN ORBIT? • When a satellite or spacecraft orbits Earth, it is moving forward but it is also in free fall. • The combination of the forward motion and the downward motion due to gravity combine to cause orbiting.