Introduction to Forces and Interactions

Representative Image

PS2: Motion and Stability: Forces and Interactions
How can one explain and predict interactions between objects and within systems of objects?

PS2.A: Forces and Motion: How can one predict an object’s continued motion, changes in motion, or stability?

Learning goals by the end of grade 5: Each force acts on one particular object and has both a strength and a direction. An object at rest typically has multiple forces acting on it, but they add to give zero net force on the object. Forces that do not sum to zero can cause changes in the object’s speed or direction of motion. (Boundary: Qualitative and conceptual, but not quantitative addition of forces are used at this level.) The patterns of an object’s motion in various situations can be observed and measured; when past motion exhibits a regular pattern, future motion can be predicted from it. (Boundary: Technical terms, such as magnitude, velocity, momentum, and vector quantity, are not introduced at this level, but the concept that some quantities need both size and direction to be described is developed.)

PS2.B: Types of Interactions: What underlying forces explain the variety of interactions observed?

Learning goals by the end of grade 5: Objects in contact exert forces on each other (friction, elastic pushes and pulls). Electric, magnetic, and gravitational forces between a pair of objects do not require that the objects be in contact—for example, magnets push or pull at a distance. The sizes of the forces in each situation depend on the properties of the objects and their distances apart and, for forces between two magnets, on their orientation relative to each other. The gravitational force of Earth acting on an object near Earth’s surface pulls that object toward the planet’s center.

Ocean Literacy Principles

Principle 6: The ocean and humans are inextricable interconnected.

Ocean Literacy Fundamental Concept: The ocean is a source of inspiration, recreation, rejuvenation, and discovery. It is also an important element in the heritage of many cultures. (OLP6c)


These concepts will be explored in this unit through the following activity and investigation:



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Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawai?i, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.