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- E. Gravitation & Astronomy
- F. Fluid Mechanics
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- H. Sound
- I. Thermodynamics
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Spring And Pulley Paradox
Purpose
To illustrate forces in a potentially paradoxical way.
Equipment
Spring scale, pulley, and spring gizmo as photographed.
Suggestions
Let your students guess before letting one read the result.
Images
Description
The mass on the hanger in the center pulls down on the spring scale with a force W equal to its weight. Q: If two identical mass hangers are connected over the two pulleys, with a spring and an identical spring scale between the pulleys, what will that spring scale read: 0, W, or 2W? Suggest that it might be zero because the spring "uses up" the force in becoming extended. Alternatively, suggest that it might read 2W because each of the two masses on the ends is pulling with a force W.
References
Richard M. Sutton, Demonstration Experiments in Physics, Demonstration M-8. Addition of Forces. George W. Ficken, Jr., and Angelo A. Gousios, A "Universal" mechanics demonstration, TPT 13, 169-170 (1975). Anton E. Lawson and Warren T. Wollman, Physics Problems and the Process of Self-Regulation, TPT 13, 470-475 (1975).
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See pagesc1. center of mass motion
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See pagesc3. first law of motion
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See pagesc4. second law of motion
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See pagesc5. third law of motion
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See pagesc6. friction
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See pagesc7. collisions
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See pagesc8. mechanical energy & power
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See pagesc1. center of mass motion
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See pagesc3. first law of motion
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See pagesc4. second law of motion
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See pagesc5. third law of motion
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See pagesc6. friction
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See pagesc7. collisions
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See pagesc8. mechanical energy & power