The hydraulic lever

What the Activity is for

Trading force and distance.

Here, pupils shift fluid from one cylinder to another, making predictions about the forces generated from the distances moved, and knowing that there is a trade off between force and distance.

What to Prepare

• the interactive object running on a number of computers, so that two or three pupils can work together around the computer (see below)
• perhaps a single copy of the interactive running on a computer connected to a large display for a plenary activity

What Happens During this Activity

Pupils follow these simple instructions for each screen. There are three separate screens, so you might like to share out the screens amongst the class, so that results can be pooled at the end.

For each screen:

• Mark on the liquid heights before.
• Choose a force for the left hand piston.
• Move fluid from one side to the other.
• Mark on the liquid heights after.
• Adjust piston heights.
• Choose an appropriate force for the right hand piston.

Then ask: Can you explain what you have just done in a way that makes it obvious why the forces you have chosen are the right ones?