Grade: 3rd Topic: Unbalanced v. Balanced Force Lesson # 1 in a series of 6 lessons
Brief Lesson Description: By playing tug of war and asking questions, students will learn about balanced and unbalanced force.
Essential Question(s): Why do objects move?
Learning Outcomes: Students will learn that an object acted on by equal forces will not be in motion. Students will learn that an object will move in the direction of the greatest force acting upon it.
NYS Science Standards: S1.1 Ask "why" questions in attempts to seek greater understanding concerning objects and events they have observed and heard about.
S1.1a Observe and discuss objects and events and record observations
S1.1b Articulate appropriate questions based on observations
5.1b: The position or direction of motion of an object can be changed by pushing or pulling.
Background Information
Materials:
2 Ropes
Student notebooks
Pencils
Adequate space for play: Gymnasium or outside space
Prior Student Knowledge:
Pushes and pulls have been introduced in previous grades
Pushes and pulls cause objects to move, change direction, change speed, or stop moving.
Possible Preconceptions/Misconceptions:
An object at rest does not have forces acting upon it
Forces acting on an object will always cause it to move
Bring the class to an open area (gymnasium, outside space) and lay down 1 of the ropes on the ground.
Ask the class if the rope is moving. How can we make the rope move? Have the students record their ideas on how they can make a rope move in their science notebook.
After a few minutes, ask if anyone would like to share their ideas. Answers could include:
Pull the rope
Throw the rope
Push the rope
Swing the rope
Lesson Description & Probing Questions:
Explain the game of tug of war, which most students probably already know.
Since teams are needed for this activity, ask the students to brainstorm about who they think should be on opposite teams. In their notebook, have them record at least two combinations of opposing teams. For example:
Boys v. Girls
Tall students v. Short students
Even teams splitting up boys/girls, short/tall, etc.
Odd numbered teams
Ask students to share their ideas in small groups of 3-4 students. Encourage question asking like, why did you choose those teams? What do you think would happen?
The teacher will go around visiting with each of the groups, and select at least 3 student ideas to test while playing tug of war.
Test out each scenario 2 or 3 times to avoid confusion and see if the result stays the same.
After each scenario, have students record the teams, and the results.
EXPLAIN: Concepts Explained and Vocabulary Defined:
As a class, discuss each scenario, and why the result happened.
Why did this team win?
Why did this round go faster than the other round?
The teacher will now begin to use the concept of force to explain what has happened in the rounds of tug of war
The rope moved in the direction of the largest force acting upon it
When the rope is laying on the ground, there are no horizontal forces acting upon it (no teams pulling) but there are equal vertical forces (gravity and ground) causing it to rest.
What would happen if we dropped the rope from eye level?
What would happen if I pick up the rope from the middle? My force is greater than the force of gravity, therefore the rope is lifted off the ground.
Vocabulary: Have students record the following vocabulary words in their journals, defining them based on the class discussion.
Force – any push or pull that changes the motion of an object
Vertical -
Horizontal
Balanced Force – two equal forces in opposite directions, acting on an object. Do not cause a change in motion.
Unbalanced – one or more unequal force(s) acting on an object. Cause a change in motion.
Extensions: As an extension, the teacher can tie a second rope to the first rope in the middle to create an X. The class can split up into 4 teams, and explore 4-way tug of war similarly to how they explored the original games. This might bring up new questions like:
What happens if all 4 teams have equal strength?
What if 2 teams worked with each other?
What if 3 teams worked with each other?
Assessment:
Observations of questions and thoughts throughout the lesson
Collection of journals with a checklist to determine understanding of lesson and concepts