Pascal's See Saw

A black and orange exhibit table, with matching information panel at the back. On the table sits two silver pistons with black handles and a purple base between them.
A black and orange exhibit table, with matching information panel at the back. On the table sits two silver pistons with black handles and a purple base between them.

Pressure applied over an area generates a force that can do work. Changing the area or the pressure increases or decreases the force.

How it works

Push down the narrow piston and watch how the attached, wider piston moves, due to transferred pressure and force over an area.

Things to try or ask around the exhibit

  • Will each piston move the same distance and with the same force?
  • Which piston moves higher?
  • Is one piston more difficult to push down than the other?

Background

The two pistons and connecting tubes are filled with air. As you push down one piston, a constant pressure moves through the air. More air is in contact with the wider piston, so it moves with more force (maybe to lift heavy items), but only over a short distance. To raise the wide piston,you need to push the narrow piston down further (but it's easier to push down). This is called magnification of force.

Finding the science in your world

Pneumatic (air-based) and hydraulic (oil or water-based) pistons are used in many ways.

When a mechanic lifts a car on a hoist, they are putting oil and air under pressure in a hydraulic lift.

When you drive a car, it uses hydraulics and pneumatics to work the brakes and steering.

The next time you see a garbage truck lifting a wheelie bin, or a giant excavator moving piles of dirt, see if you can spot their moving pistons.