Newton’s Cradle

This is an attempt to construct a “Newton’s Cradle” for the Executive Toy Secretary’s Challenge.

This one is so called because it demonstrates, to some extent, Newton’s Laws of Motion. Wikipedia, the online encyclopaedia, has this to say:

Newton’s laws of motion are three physical laws which provide relationships between the forces acting on a body and the motion of the body. They were first compiled by Sir Isaac Newton in his work Philosophiae Naturalis Principia Mathematica (1687). The laws form the basis for classical mechanics and Newton himself used them to explain many results concerning the motion of physical objects. In the third volume of the text, he showed that these laws of motion, combined with his law of universal gravitation, explained Kepler’s laws of planetary motion.

Briefly stated, the three laws are:

  1. A physical body will remain at rest, or continue to move at a constant velocity, unless an external net force acts upon it.
  2. The net force on a body is equal to its mass multiplied by its acceleration.
  3. For every action there is an equal and opposite reaction.

The model doesn’t work as well as a commercially available Newton’s Cradle. This is because I have had to use chimney adaptors with a ½” brass pulley inside instead of the steel balls that would be used. The contact area between the adjoining chimney adaptors varies between each — if balls had been used the contact area would be the same in each case, and always at the mid-point.

What is supposed to happen is that if you draw back one object and let it go, when it strikes the remaining static ones the one on the opposite side will move while all the others remain stationary. Draw two back and two will move away, etc. With the model, the energy is not transferred smoothly across and this tends to result in a rather haphazard movement.

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