Push-Me-Pull-You

a simple hydraulics system

 

 

 

Category - Force & Energy

Key Idea - Hydraulics

 

Purpose - Hydraulics are very easy to demonstrate with this simple contraption.
Nature -  Demo with student help.
Materials -  aquarium hose, 50 ml and a 10 ml syringes, water
Method - 
  1. Connect up the two syringes with about 60 cm of aquarium hose as shown.
  2. Draw water into the system leaving as little air as possible (Not as easy as it sounds).  It works best if the 50 ml syringe is pushed completely in and the 10 ml syringe is almost full.

  1. Note that as you push the small syringe the big one is forced to move out.  You can see how hydraulics is good for transferring force through all sorts of shapes by using a flexible hose.

  2. Also note that the large syringe moves a very small distance compared with the small one.  Get a student to try to hold in the large syringe with both hands using all of their strength, while you push on the small using one hand a minimal effort.  The student will be unable to stop the large syringe moving out.

 
Safety - Nil
Explanation - As a simple machine, this set up demonstrates the fact that a trade can be made between the distance a force needs to travel with the effort required.  The smaller syringe may need to travel further but less effort is needed to move it that distance.  This is the same with other simple machines such as pulleys, inclined planes and levers.
Notes - Make sure to connect the syringes to the hose well.  I have had the pressure cause the hose to pop off spraying me with water!!