First Class Levers: Investigating the Relationship Between the Force of Effort, Force of Resistance, and the Placement of the Fulcrum
Initial Publication Date: September 4, 2008
Summary
In this classroom activity, students investigate the relationship between the two forces and the location of the fulcrum in a first class lever. Students work in cooperative groups of approximately three to make observations that they can then generate a formula for, determining the relationship between the force of effort, force of resistance, and location of the fulcrum.
Learning Goals
Goals:
1. Students will devise the relationship between the force of effort, the force of resistance, and the location of the fulcrum in a first class lever.
2. Students will be able to explain what a first class lever is.
Key Concepts:
1. A first class lever is a type of simple machine in which the fulcrum is positioned between the force of effort and the resistance.
2. For a first class lever, FR x DR = FE x DE
Key Vocabulary:
1. Force of Effort
2. Force of Resistance
3. Fulcrum
4. First Class Lever
1. Students will devise the relationship between the force of effort, the force of resistance, and the location of the fulcrum in a first class lever.
2. Students will be able to explain what a first class lever is.
Key Concepts:
1. A first class lever is a type of simple machine in which the fulcrum is positioned between the force of effort and the resistance.
2. For a first class lever, FR x DR = FE x DE
Key Vocabulary:
1. Force of Effort
2. Force of Resistance
3. Fulcrum
4. First Class Lever
Context for Use
This activity was developed for 9th grade alternative students in a physical science class, but it could be used at the middle school level with few changes. This is a good first activity for teaching the simple machines as it allows students to figure out the equation for themselves and values reason and common sense. This activity can be used the first or second day of simple machines after introducing force, resistance, and the types of simple machines. It should take no more than 20-30 minutes. Each group requires one meter stick, three meter stick clamps, a rope or stand to use as fulcrum, a spring scale, and weights (at least three: one 100 g, one 200 g, and one other).
Description and Teaching Materials
The students will begin by attempting to figure what the simple machines are as a class and take notes on the key vocabulary terms. At this point few instructions are given. Students are divided into their lab groups and each group picks up the necessary materials. The "First Class Levers Lab #1" sheet is handed out and students are directed to begin the activity without any additional instruction. In this lab activity students move the fulcrum of a first class lever to demonstrate the relationship between the force of effort, force of resistance, and the location of the fulcrum. Once students finish the activity the entire class comes back together to share observations and deduce the formula.
Teaching Notes and Tips
There are very few safety needs other than making sure students handle the meter sticks responsibly. Students rarely struggle with the completion of this activity, but frequently can describe the relationship orally but not mathematically. At first they may need assistance in reaching this new step.
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Assessment
Students will be assessed at this time on their completion of the group activity/lab.
Standards
Grades 9-12, Physical Science D. Motion, 1