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Lever to lift a marble using the weight of water

Set up a lever that lifts a marble at one end by pouring water into a bucket at the other.
Science content (2016 curriculum): 
Physics: Motion and Forces, Newton’s Laws, Gravity (K, 2, 6)
Physics: Simple and complex Machines (5)
  • small chair
  • light, strong 4ft rod e.g. 5/16" diameter wooden stick
  • two small hooks, secured at each end of the rod, facing the same way
  • about 50cm string for lashing rod to chair
  • bucket - handle may be too high so replace with shorter string handle
  • jug for carrying water
  • sink
  • tray to catch spills under the bucket
  • small pot e.g. dollar store plastic shot glasses
  • marble
  • masking tape
  • cloths and mops for spills

Challenge the students to raise a marble to table height with out without picking it up with their hands. can only pour water, and the weight of the water will lift the marble. This activity uses a lever.

Turn chair over and put on the floor so the legs are in the air.
Show students how to place the rod on the end of a leg so that it rests in the nook before the foot, and lash it loosely so that the rod stays in place but can slide through the string lashing.
Instruct students that they will hang a bucket from the end of the rod at the chair, then pour water into it until it raises the other end of the rod.
Show students how to make a handle on a small pot with masking tape, place a marble in it, and how to hang on the hook furthest from the chair.
Show them how by sliding the rod through the string, they can change the position of the pivot point, or fulcrum, and therefore how high each end of the rod can go.

Allow students to work in pairs or small groups for a while. They may need assistance with adjusting how tightly the rod is lashed to the chair leg - too much friction prevents the marble pot at one end of the rod from swinging up to its full height.

As s group discuss challenges and how they overcame them.
The marble can be successfully lifted when the fulcrum is very near the bucket of water, so that the other end holding the marble can swing up high enough to reach the table top.
Review how a lever works: a lot of force at one end moving a small distance (the bucket full of water) produces a smaller force over a greater distance at the other end (hence the lighter load of the marble can be lifted high enough to reach the table top).
Relate to other levers students might be familiar with e.g. see saw.


Optional: students can add a roller coaster for the marbles to return to floor level.

Grades taught: 
Gr K
Gr 2
Gr 3
Gr 4
Gr 5
Brenda Koch
Fiona Laporte
Teaching site: 
Xpey' Elementary School (formerly MacDonald Elementary)
Activity originally developed and delivered: 

Aboriginal Focus School with the Vancouver School Board's Scientist in Residence Program