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Home » Lecture Demonstration Manual » 1. Mechanics » D. Third Law

Table of Contents

  • 1. Mechanics
    • A. First Day Demos
    • B. First Law, Inertia
    • C. Second Law
    • D. Third Law
      • 10. Ballistocardiograph
      • 20. Paradox of Forces
      • 30. Rockets
      • 40. Sail and Prop
    • E. Angular Momentum
    • F. Ballistics
    • G. Center of Mass Demonstrations
    • H. Energy
    • I. Friction
    • J. Gravitational Acceleration
    • K. Kinematics
    • L. Momentum and Collisions
    • M. Nonlinear Mechanics
    • N. Rotational Inertia
    • O. Statics
    • P. Torque
    • Q. Uniform Circular Motion
    • R. Vectors and Forces
    • S. Data Studio
  • 2. Harmonic Motion, Waves and Sound
  • 3. Matter and Thermodynamics
  • 4. Electricity and Magnetism
  • 5. Light and Optics
  • 6. Modern Physics
  • 7. Astronomy
  • 8. Software and Multimedia
  • 9. Index and code conversion from older manual
  • External Resources

20. Paradox of Forces

A 1 kg mass weighs 9.8 N as checked by a spring scale. Two 1 kg masses are hooked on the ends of a string which is passed over a pair of pulleys, and the spring scale is placed in the center of the string to measure the tension as shown. The scale is covered with a cloth to hide its reading, and the class is then asked to predict whether the scale will read 0, 9.8, or 19.6 N.

‹ 10. Ballistocardiograph up 30. Rockets ›
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