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Inclined Plane - Screw

Name of Corresponding Unit Plan: Inclined Plane - Uses; Inclined Plane - Pull Weight

Grade Level: 2-8

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: 30-50 minutes

Learning Goals: Students will recognize screws as inclined planes wrapped around an axis.

Description/Sequence:

  1. The teacher should review that inclined planes achieve mechanical advantage by lifting a resistance over a distance.
  2. Cut out a paper triangle representing an inclined plane profile. A 1:10 ratio is good although it need not be exact. Calculate the mechanical advantage of the inclined plane using the formula Effort Distance/Resistance Distance.
  3. Roll the paper triangle around a rod. Note that the hypotenuse of the triangle now forms a spiral up the rod. Point out that the inclined plane has the same length and rise, but is now twisted into a spiral.
  4. Introduce the terms Circumference and Threads. Note that the calculation for mechanical advantage can now be made using the circumference of the shaft as the effort distance and the distance between threads as the resistance distance. The result is the Pitch of the screw.
  5. Show examples of actually screws of different sizes (wood screw, large bolt, threaded end of brook handle, scissor jack, etc.)
  6. Point out that the size of the screw is not important in determining mechanical advantage. The important factor is the pitch.

Assessments Informal assessment based on participation and general understanding.

Materials/Resources: Paper triangle, collection of screws and bolts of different sizes

Special Considerations: For larger groups it is helpful to draw a bold line along the hypotenuse of the paper triangle before it is rolled onto the rod.