Use this science lesson plan as part of your motion lesson plans including Newton's Laws of Motion. This motion lesson plan focuses on Newtons' First Law of Motion.

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### Students in Motion

Before beginning this motion lesson plan, review the Introduction to Newton's Laws of Motion lesson plan along with the Motion Lesson Plan to get students familiar with the concept of motion. Once students appear to familiar with the concept of motion, follow the instruction below to use this lesson plan to discuss Newton's First Law of Motion.

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### Unbalanced Forces in Motion

For this activity you will need a piece of rope about ten feet long. Follow the instruction below to complete the activity.

- Ask for two student volunteers.
- Ask students to each grab and opposite end of the rope.
- Ask students to each pull the rope so that the rope is taut, but neither student is moving from their original position.
- Explain to students that the velocity of the rope is at a quantity of zero at the moment because there is no motion in either direction, though there is force being applied in both directions.
- Ask students to explain why the velocity is zero. Allow students to discuss possible conclusions. Once students have discussed possible conclusions, present them with the idea of balanced forces.
- Explain that the rope is not in motion because the students were applying balanced forces, thus each force cancels the other out in a manner of speaking.
- Introduce Newton's First Law of Motion: An object will remain at rest or in uniform motion in a straight line unless acted on by an external unbalanced force.

Discuss the term

*unbalanced force*with the students. Explain that balanced forces in essence apply the same amount of force to an object tin opposite directions so that the object will not move in either direction. Unbalanced forces are forces that are unequal in some way so that motion is created by the stronger force.- Ask students to apply all of their force to the rope until one student is forced to move.
- Once the student is force to move, explain that the unbalanced force of the stronger student caused the motion of the rope, which in turn caused a motion of the other student.
- Ask students to again pull the rope taut and lean slightly back.
- Ask one student to release some of their force on the rope. The rope should go slack and the other student may even stumble back a step or two.
- Explain that this is another method of unbalanced force. The student who stumbled back did so because when they were both pulling on the rope, the forces were balanced, but when the other student loosened their grip on the rope, the forces became unbalanced and the student stumbled back as a result.

This motion lesson plan should have given students an idea of the concept of Newton's First Law of Motion and in particular, an increased understanding of balanced and unbalanced forces. For more information on Newton's First Law of Motion, or to reinforce student's understanding of Newton's First Law of Motion, see this Newton's First Law of Motion Study Guide.