A pair of syringes
Classroom Activity
for 11-14
What the Activity is for
Feeling the forces in a system, where fluids link two different pistons.
Here pupils can feel for themselves the change in forces that results from a change in area, relating this to the number of collisions of particles within the pistons.
What to Prepare
- one large and one small diameter syringe, connected by plastic tubing (air works well enough as the linking fluid – water gets messy)
What Happens During this Activity
Introduce the apparatus. Tell the class that they are going to push down on the larger of the two plungers. Draw their attention to the different areas, and so the different numbers of particles colliding with the surface. Ask them how hard they'll have to push on the smaller plunger (choosing from: same force, less force, more force), to balance the two plungers. Then ask them to justify their assertion. Then hand out the apparatus and allow them to explore the effect and to relate their prediction to the forces they exert on the two pistons.
