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By the end of the 2nd grade, students should know that: Things near the earth fall to the ground unless something holds them up. 4G/P1
By the end of the 5th grade, students should know that: The earth's gravity pulls any object on or near the earth toward it without touching it. 4G/E1
By the end of the 8th grade, students should know that: Every object exerts gravitational force on every other object. The force depends on how much mass the objects have and on how far apart they are. The force is hard to detect unless at least one of the objects has a lot of mass. 4G/M1
The sun's gravitational pull holds the earth and other planets in their orbits, just as the planets' gravitational pull keeps their moons in orbit around them. 4G/M2
By the end of the 12th grade, students should know that: Gravitational force is an attraction between masses. The strength of the force is proportional to the masses and weakens rapidly with increasing distance between them. 4G/H1
National Science Education Standards
Properties of Objects and Materials
Objects have many observable properties, including size, weight, shape, color, temperature, and the ability to react with other substances. Those properties can be measured using tools, such as rulers, balances, and thermometers.
Position and Motion of Objects
The position of an object can be described by locating it relative to another object or the background.
An object's motion can be described by tracing and measuring its position over time.
The position and motion of objects can be changed by pushing or pulling. The size of the change is related to the strength of the push or pull.
As a result of their activities in grades 5-8, all students should develop an understanding of Motions and Forces
If more than one force acts on an objects along a straight lines, then the forces will reinforce and cancel one another, depending on their direction and magnitude. Unbalanced forces will cause changes in the speed or direction of an object's motion.
EARTH AND SPACE SCIENCE:
Earth in the Solar System
Most objects in the solar system are in regular and predictable motion.
Gravity is the force that keeps plants in orbit around the sun and governs the rest of the motion in the solar system.
Motions and Forces
Objects change their motion only when a net force is applied. Laws of motion are used to calculate precisely the effects of forces on the motion of objects. The magnitude of the change in motion can be calculated using the relationship F = ma, which is independent of the nature of the force. Whenever one object exerts force on another, a force equal in magnitude and opposite in direction is exerted on the first object.
Gravitation is a universal force that each mass exerts on any other mass. The strength of the gravitational attractive force between two masses is proportional to the masses and inversely proportional to the square of the distance between them.
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