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The catapult

The catapult
Materials and mounting
instructions:
  a spoon, a spring, a support, a light ball made of plastic material or of pressed paper. Fix, with glue or scotch tape, the spring and the end of the spoon to the support and fix the top of the spring to the spoon right below the scoop. For applications to energy studies, prepare two catapults with springs of different stiffness.
How to play:   hold the support with one hand, with the other hand push down the spoon, then release it rapidly.
Physics:  
  • force and interaction: the force is characteristic of the interaction between the hand and the spring and we identify it by its “effects” (compression),
  • while we apply a force to the spring, the spring applies in turn a force to our hand (action and reaction),
  • the distance of the throw does not depend only on the force but on the force times the extent of the compression, that is on the energy which is transferred from the hand to the spring and from the spring to the ball,
  • energy has different forms.
Educational aspects:  
  • discover force and interaction and different types of forces (Fa),
  • discover action and reaction (Fd),
  • analyse the relation between force, compression and distance of the throw to understand the difference between force and energy (best done with springs of different stiffness- Ea),
  • discover the properties of energy : energy can have different forms (Eb) and can be transferred (Ec),
  • measure length and distance (Sa),
  • compare with your expectations.
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Last modified: Thu Nov 16 09:33:24 CET 2000