Grade 3 Science, NGSS Unit 2 Force and Motion In this unit of study, students are able to determine the effects of balanced and unbalanced forces on the motion of an object. The crosscutting concepts of patterns and cause and effect are called out as organizing concepts for these disciplinary core ideas. In the third-grade performance expectations, students are expected to demonstrate grade-appropriate proficiency by planning and carrying out investigations. Students are expected to use these practices to demonstrate understanding of the core ideas.
• How do equal and unequal forces on an object affect the object?
Driving question 1 What are the effects of balanced and unbalanced forces on the motion of an object?
Science investigations use a variety of methods, tools, and techniques.
• Cause-and-effect relationships are routinely identified.
• Objects in contact exert forces on each other.
• Each force that acts on a particular object has both 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. (Qualitative and conceptual, but not quantitative, addition of forces are used at this level.
Identify cause-and-effect relationships.
• Plan and conduct investigations collaboratively to produce data to serve as the basis for evidence.
• Use fair tests in which variables are controlled and the number of trials considered.
• Plan and conduct an investigation to provide evidence of the effects of balanced and unbalanced forces on the motion of an object. (Assessment is limited to one variable at a time: number, size, or direction of forces. Assessment does not include quantitative force size, only qualitative and relative. Assessment is also limited to gravity being addressed as a force that pulls objects down.) Examples could include: − An unbalanced force on one side of a ball can make it start moving. − Balanced forces pushing on a box from both sides will not produce any motion at all.
Driving question 2
How can patterns be used to predict the motion of object?
Science findings are based on recognizing patterns.
• Patterns of change can be used to make predictions.
• 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. (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.)
Make predictions using patterns of change.
• Make observations and/or measurements to produce data to serve as the basis of evidence for an explanation of a phenomenon.
• Make observations and/or measurements of an object’s motion to provide evidence that a pattern can be used to predict future motion. (Assessment does not include technical terms such as period and frequency.) Examples of motion with a predictable pattern could include: − A child swinging in a swing. − A ball rolling back and forth in a bowl. − Two children on a seesaw