Gravity and Motion

I. Gravity force- a push or pull. Gravity- Attracts all objects to each other. a. pulls moon toward Earth. b. pulls planets toward sun. c. measured in Newtons. 3. Forces on earth are the same as everywhere in the univers. 4. Law of universal gravitation- every object in the universe attracts to every other object.

Gravity, Mass, and Weight 4. The strength of the force of gravity btwn two objects depends on 2 factors: a. mass of the objects b. distance btwn them. Gravity, Mass, and Weight 1. mass- amt of matter in an object. 2. Smaller mass will have smaller gravity or pull. 3. Larger mass will have larger gravity or pull 4. Earth pulls on moon and moon pulls on Earth. 5. weight- force of gravity on an object. a. can change depending on location.

On the moon, you wld weigh 1/6 of you weight on Earth. Why On the moon, you wld weigh 1/6 of you weight on Earth. Why? Moon is much less massive than Earth, so the pull of moon’s gravity on you wld be less than pull of Earth’s gravity. Ex: If you weight 100 lbs on Earth, you would weigh 16.7 lbs on the moon. You have the same mass (you are made up of the same amt of stuff, you just weigh different).

Moon Gravity

B. Gravity and Distance The strength of the gravity is affected by the distance btwn two objects as well as their masses. As distance increases, gravity decreases.(The farther away you are from an object, the less it will pull on you.) Ex: Earth is far away from Pluto so there is not much pull from it.

www.brainpop.com gravity Lmscatoosa pw: warriors

II. Intertia and Orbital Motion Inertia- tendency of an object to resist a change in motion. The more mass an object has, the greater its inertia. Ex: you are riding in a car and the car stops, you go forward. Your body wants to continue moving after the car stops. Newton’s 1st Law of Motion- object at rest will stay at rest and an object in motion will stay in motion in a straight line and at a constant speed, unless there is an outside force.

B. Orbital Motion Two factors, inertia and gravity, combine to keep Earth in orbit around the sun and the moon in orbit around Earth. Earth’s gravity keeps pulling moon toward it. At the same time, moon keeps moving ahead because of its inertia. If not for Earth’s gravity, inertia would cause the moon to move off through space in a straight line. Earth revolves around the sun b/c sun’s gravity pulls on it while Earth’s inertia keeps it moving ahead.

Inertia and earth’s gravity \\Lmsadms2\vol1\PERSONAL\hmoorman\earth science videos\intertia Earth_inertia -A_Spin_Around_the_Solar_System__How_the_Solar_System_Works.asf

www.youtube.com bill nye planets and moons and frame of reference law of inertia. http://www.youtube.com/watch?v=ZFoG7HRF2mE