Gravity and Motion Section 2: Pages 666 -669

Earth In Space review 2 major motions of the earth are? Which motion causes day and night? What causes the seasons? What tilt is the earth at? What are solstices and equinoxes? How do solstices and equinoxes relate to seasons? How would seasons be different if Earth were not tilted?

Why Doesn’t the Moon fly off into Space? There must be a force acting between the two objects A force is something that influences change Isaac Newton identified that there must be a force acting between earth and moon Force that keeps moon in orbit different than forces we are influenced by everyday. Why?

Gravity Gravity is a force that attracts all objects towards each other Newton did not discover gravity, only realized it as a universal force Gravity is measured in newtons Law of Universal Gravitation (Newton) states that every object in the universe attracts every other object The strength of the force of gravity depends on two things: Mass and Distance

Gravity, Mass and Distance

Gravity, Mass and Distance Mass amount of matter in an object Mass never changes Weight is the force of gravity on an object Changes with gravity My mass is 87.91 kg, my weight is 200 pounds Moon’s gravity is 1/6 of earth: what is my mass and weight? Mass Increases force of Gravity Increases Distance increases force of Gravity Decreases

Why doesn’t Earth crash into the Sun? Must be another force acting Inertia ability of an object to resist change in motion Newton’s First Law of Motion states that an object at rest will stay at rest and an object in motion will stay in motion with a constant speed and direction unless acted upon by a force.

Why do Earth and Moon remain in their Orbits? 2 factors: Inertia and gravity Gravity pulls objects towards each other, preventing the moon from going in a straight line Inertia makes the moon move forward The combination creates the orbit

Planetary Orbits

Gravity and Motion Review What is the law of universal gravitation? What two factors determine the force of gravity between two objects If the moon was closer to Earth, how would the force of gravity between the Earth and moon be different? What two factors act together to keep Earth in the orbit around the sun? Why doesn’t Earth simply fall into the sun? How would Earth move if the sun suddenly disappeared? Explain your answer.