I@Pht Home Page  

The rope pull

The rope pull
Materials and mounting
instructions:
  a long rope, a flag, an anti-slip mat.
How to play:   fix the flag in the middle of the rope. Ask two students to grasp the two ends of the rope, then stretch it and pull in opposite directions, while standing in their fixed positions on the floor. Each student must try to drag the other towards his position by advancing his grip on the rope until he reaches the flag First let them pull the rope while standing on a smooth floor, then ask them to repeat after putting the anti-slip mat under the feet of one of the students, preferably the “weaker” one.
Physics:  
  • force and interaction: the “apparent” forces are the muscular forces applied by the students to the rope, but there are many other forces (the elastic force, the forces applied by the students to the floor and by the floor to the feet, the gravity forces, etc.)
  • each force acts along a given direction,
  • when the student pulls the rope, the rope applies to him/her an opposite force (red arrow), because of the principle of action and reaction,
  • since the student pushes on the floor, the floor applies to him/her an opposite force (black arrows), because of the principle of action and reaction,
  • the composition of the black and red arrows gives the resultant force applied to the student,
  • since the rope applies equal forces at the two ends, the red arrows are equal and opposite, the forces which are different are those applied by the floor (blue arrows) and “wins” the student who succeeds in applying the larger force to the floor,
  • when one of the students drags the other, energy is transferred and transformed mainly into kinetic energy of the student who is dragged.
Educational aspects:  
  • discover force and interaction and different types of forces (Fa),
  • discover direction of forces (Fc),
  • discover action and reaction (Fd),
  • analyse force composition (Fc),
  • explore the relation between force and energy (Ea),
  • explore energy transfer (Eb),
  • explore energy transformation (Ec),
  • compare with your expectations.
Giocattoli Home Page I@Pht Home Page

IAPhT WebMaster
Last modified: Thu Nov 16 10:29:35 CET 2000