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Benchmarks

• Changes in speed or direction of motion are caused by forces. 4F/E1a

• The greater the force is, the greater the change in motion will be. The more massive an object is, the less effect a given force will have. 4F/E1bc

By the end of 8th grade, students should know that

• An unbalanced force acting on an object changes its speed or direction of motion, or both. 4F/M3a

• If a force acts towards a single center, the object's path may curve into an orbit around the center. 4F/M3b

By the end of 12th grade, students should know that

• The change in motion (direction or speed) of an object is proportional to the applied force and inversely proportional to the mass. 4F/H1*

National Science Education Standards

Grades K-4
PHYSICAL SCIENCE -- CONTENT STANDARD B
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.

Grades 5-8
PHYSICAL SCIENCE -- CONTENT STANDARD B
Motions and Forces

• The motion of an object can be described by its position, direction of motion and speed. That motion can be measured and represented on a graph.
• An object that is not being subjected to a force will continue to move at a constant speed and in a straight line.
• If more than one force acts on an object along a straight line, then the forces will reinforce or 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 -- CONTENT STANDARD D
Earth in the Solar System

• The Earth is the third planet from the sun in a system that includes the Moon, the sun, eight other planets and their moons, and smaller objects, such as asteroids and comets. The sun, an average star, is the central and largest body in the solar system.
• Gravity is the force that keeps planets in orbit around the sun and governs the rest of the motion in the solar system. Gravity alone holds us to the Earth's surface and explains the phenomena of the tides.

Grades 9-12
PHYSICAL SCIENCE -- CONTENT STANDARD B
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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