M5 The Pendulum


Law of falling bodies describes how objects fall. Objects in vacuum fall at the same rate while elsewhere, they do not. The rate at which objects fall depends only on whether they are in a vacuum or not. Their mass or weight or shape has no impact on their acceleration.

Discrepant Event: The Pendulum

If, in a vacuum, you hang two objects of the same mass by two string of the same length they will swing in time with one another. If you increase the length of one string, lift both to the same height and let them go at the same time, the one attached to the longer strings takes longer to return to its starting point. Conduct the same test, but this time you increase the mass of one of the objects keeping the length of the strings the same, contrary to what you might think happens, there is no difference in the time they take to make one swing. Why?

Concepts involved:

  • Gravity, mass, speed/rate of change of speed, rate of falling, acceleration, law of falling bodies, resistance, surface area.
  • (Pendulum related concepts: distance/displacement/amplitude/angle, period, equilibrium position.)

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