Investigation Question:  What makes an object start to move?

Key Concepts:

1. A force acts between two objects.

2. When an object starts moving or stops moving, that is evidence that a force has acted on it. 

Chapter Overview: 

Students are introduced to a fictional scenario—the citizens of the city of Faraday are excited to hear that a new train service will be built for their city, but they become concerned when they hear that the train will be a floating train. Students are challenged to figure out how the floating train works in order to explain it to the citizens of Faraday.  After watching a brief animation of the train, the class begins by investigating the question Why does the train rise?  Using simple materials, students observe what makes an object start to move. They learn that the pushes and pulls by one object on another are called forces and that a force can make an object start moving. They further investigate forces and discover that when you observe an object start to move or stop moving it is evidence that a force is acting on it. Based on evidence from their investigations, students conclude that a force acts between two objects. They reflect on their learning about forces by creating a chain reaction and analyzing the forces involved and by writing an explanation as a class of why the train rises—a force must act on it to make it rise. The purpose of this chapter is for students to understand what constitutes evidence of a force acting on an object; discover that a force acts between two objects; and gain initial experience with setting a purpose for investigating and with constructing explanations. 

Investigation Question 1:  How can a force act without objects touching it?

Investigation Question 2:  In what ways can magnetic force make an object move?

Key Concepts:

1. Some forces happen between objects that are touching. Other forces happen between objects that aren’t touching. 

2. Non-touching forces can act between magnets and some, but not all, other objects.

3. Magnets can attract or repel other magnets. 

4. Magnets can attract some metal objects. 

Chapter Overview:

Students are introduced to the Chapter 2 Question, Why does the train rise without anything touching it? Students plan and conduct investigations, and discover evidence of non-touching forces that involve magnets. Students gather evidence about what magnets attract and repel both from a physical investigation and by reading. By analyzing their data and diagramming forces, students begin to observe a pattern—magnets attract other magnets and some (but not all) metal objects. They also discover that magnets can repel other magnets. At the end of the chapter, students apply what they learned about magnetic force to more fully explain why the train rises. The purposes of this chapter are for students to understand that there are touching and non-touching forces, including magnetic force.

Investigation Question:  What makes an object fall?

Key Concepts:

1. An object falls because Earth pulls the object toward it with the force of gravity. 

Chapter Overview:

Students work to figure out the question Why does the train fall? When the train falls, it moves. Therefore, there must be a downward force acting on it. Students investigate what makes objects fall, and find out about gravity, a second non-touching force. They discover that an object falls because Earth pulls the object toward it with the force of gravity. Students reflect on what they have learned about touching forces, magnetic force, and gravity by creating chain reactions that involve all three types of forces, by diagramming examples of forces, and by writing to compare magnetic force and gravity. At the end of the chapter, students apply what they learned about gravity to explain and model why the train falls. The purpose of this chapter is for students to discover that gravity is a non-touching, attractive force, that, like other forces, acts between two objects. 

Investigation Question:  Why would an object not move even though a force is acting on it?

Key Concepts:

1. Two forces can be exerted on an object at the same time. 

2. When two forces are exerted on an object in opposite directions, the forces can be balanced. 

Chapter Overview:

Students work to figure out the question Why does the train float, even though gravity is acting on it? They discover balanced forces as they investigate how two forces, gravity and magnetic force, can act on an object at the same time. They investigate how a touching force or a magnetic force can keep an object from falling. Students use what they have discovered to model and write an explanation of why the train floats, and to diagram balanced forces. The purpose of this chapter is for students to understand that multiple forces can act on an object at the same time and that these forces can be balanced, which means the motion of the object will not change. This chapter provides more opportunities for students to use the concept of cause and effect and to make and use models to make sense of forces. 

Investigation Question:  What can make forces not be balanced anymore?

Key Concepts:

1. If forces are balanced, and then a force is changed, the forces become unbalanced, which can cause an object to start moving. 

Chapter Overview:

Students investigate one more change in the train’s movement. They learn how forces can become unbalanced, and use their understanding to explain why the train changes from floating to falling. They observe a demonstration of electromagnets and read about them in the reference book. The question of the floating train is wrapped up as students create final diagrams using the Force Diagramming Tool and write a final scientific explanation. The purpose of this chapter is for students to discover unbalanced forces through investigations and models, to apply what they have learned about forces to the floating train, and to extend their thinking about cause and effect.