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Levers - Seesaw

Name of Corresponding Unit Plan: Levers - Balancing

Grade Level: K-6

VT Grade Expectations
VT S:21 Students demonstrate their understanding of Force by investigating variables that change an object's speed, direction, or both, and identifying and describing the forces that cause the change in motion.

NY Standards
NY Standard 1: Scientific Inquiry
Key Idea 1: Clarify ideas through reasoning, research, and discussion

Content Areas: Science

Recommended Length/Duration: 15-30 minutes

Learning Goals: Students will discover that a lever can be balanced in a variety of ways. A longer lever requires a smaller weight to balance a heavier weight on a shorter lever.

Description/Sequence:

  1. Teacher will place students in a circle around a sturdy seesaw and discuss how a seesaw is a lever system with a fulcrum and lever arms. People provide the balancing weights for each end.
  2. Select two students of about the same size to sit on the seesaw. Observe what happens and discuss why one side went down or the seesaw was balanced.
  3. Select two students of very different sizes to sit on the seesaw. Again discuss what happens.
  4. Add another one or two students to the seesaw seats and discuss what difference the additional weight makes.
  5. Invite two students of very different size to sit on the seesaw. Have students predict what will happen and then confirm their observations.
  6. Have the heavier student slowly move toward the fulcrum until the seesaw is balanced. Point out that the weights are different, but it can be balanced by shortening the lever arm distance of the heavier weight.
  7. Have several combinations of students take turns finding their balance point. Note the relative weights of the students and distances from the fulcrum of the seesaw.
  8. After everyone has had a turn, ask if students can generalize a rule about weights and distances needed to balance the seesaw.

Assessments: Informal assessment based on participation.

Materials/Resources: Sturdy seesaw with adjustable seating. If your school does not have a playground seesaw, or if your students feel too mature to use one, this activity may be done in the classroom with a sturdy plank (2x8x8 minimum) and a block to serve as a fulcrum.

Special Considerations: Review safety precautions – always have the lighter person get off the seesaw first.