Lesson 5 Gravity View this video about gravity

Lesson 5: Gravity View this video about gravity and inertia. http: //studyjams. scholastic. com/studyjams/science/solarsystem/sgravity-and-inertia. htm

Lesson 5: Gravity A pulling force that attracts objects to one another. All objects have a gravitational pull on other objects. Strength depends on 2 factors: Product of the masses of the objects Distance between the objects

Lesson 5: Gravity Ex. If mass increases, then the pull of gravity will increase. If distance increases, then the pull of gravity will decrease.

Orbits In our solar system, planets revolve around the sun, and moons revolve around the planets. Their paths are called orbits. Earth travels in an orbit around the sun. The Moon travels in an orbit around the Earth.

Orbit Shape *Orbits are not circles. * Orbits are slightly egg-shaped, which is called an ellipse, or elliptical orbit.

Inertia The tendency of objects to keep doing what they are already doing. If an object is already in motion, it will stay in motion at that same speed and direction unless an outside force stops it. This is called Newton’s first law of motion.

Inertia would cause a planet to keep moving in a straight path, but an outside force must act on it in order for it to stay in orbit. • This outside force is gravity. • The gravitational pull of the sun pulls the planet inward while the planet’s speed and directions pushes it outward. • When these are in balance, the planet remains in a curved path around the sun.