Museum Hours
Thu: 1 PM–8 PM
Fri–Mon: 10 AM–5 PM
Tue–Wed: Closed
200 Larkin Street
San Francisco, CA 94102

Okamura’s Extended Cup Platform

Inspired by Arthur Okamura’s “The Extended Knife Platform.”

Extended knife platform activity.

“There was a time when kids (and even grown-ups) were able to spend hours using simple items, found in any household, making objects that were silly and fun.  Things didn’t need batteries and they were not based on TV characters; they were just things you did together on a kitchen table, or a back porch, but the best part was that there was a bit of mystery in them – they were tricks, and they were wonderful!”

– Arthur Okamura, Paper Propeller, the Jumping Frog, the Spinning Quarter: And 38 Other Amazing Tricks You Can Do With Stuff Lying Around the House


As a magician, Arthur Okamura wrote and illustrated his own magic trick books, including Paper Propeller, the Jumping Frog, the Spinning Quarter: And 38 Other Amazing Tricks You Can Do With Stuff Lying Around the House.  In this activity, you will complete one of his physical balance tricks and suspend one cup above or at the same height of three other cups. 

Learn More about Arthur Okamura:


You will:

  1. Observe gravitational force exerted by Earth and properties of objects’ center of weight;
  2. Form a hypothesis about how to balance a cup above or at the same height of the other three cups;
  3. Design an experiment to test your hypothesis;
  4. Collect and analyze data;
  5. Draw conclusions based on your analysis.

Content Standards (California)

Writing Standards (Grade 4 and 5):
W.5.7: Conduct short research projects that use several sources to build knowledge through investigation of different aspects of a topic. (5-PS1-2),(5-PS1-3),(5-PS1-4)

Science Standards (Grade 4 and 5):
3–5-ETS1-1: Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost. 
3–5-ETS1-2: Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem. 
3–5-ETS1-3: Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.
5-PS2-1 Support an argument that the gravitational force exerted by Earth on objects is directed down.


Four cups of the same height

Three knives (dull or plastic) or wooden popsicle sticks

Observation Table (under Downloads)

Worksheet (under Downloads)

Other materials to build the final device if desired

Safety Precautions

  • Frequently observe the placement of materials to avoid falls or injuries.  
  • Use durable objects, as they will fall from a height and have the potential of breaking.
  • Adult supervision is advised.


Hypothesis: (noun) an educated prediction or explanation that can be tested in an experiment.
Objective: (noun) a goal or end of action.
Evidence: (noun) that which tends to prove or disprove something; ground for belief; proof.
Observation: (noun) the act of gathering information of the outside world through the five senses (sight, sound, smell, touch and taste), or recording information using scientific tools and instruments.


  1. Based on the objective, write the steps on how you are going to successfully suspend one cup above or at the same height of the other three cups using three knives or wooden popsicle sticks.  Make sure that your procedures are clear enough so that someone else, like your classmate or sibling, can replicate your experiment.
    (Note: The one cup suspended in the air cannot touch the other three cups.  While possible without, you may include other objects to build your device.)
  2. Draw how you imagine the successful final product will look like.  Give it a name.
  3. Make a hypothesis on whether or not your device will work and explain your rationale.
  4. Follow your procedures.  Write and draw your observations in the Observation Table (under Downloads) while you conduct your experiment.
  5. After the first attempt, adjust procedures to improve your device.  Repeat steps 2-4.
  6. After the second attempt, adjust procedures again to improve your device.  Repeat steps 2-4.
  7. Write your results with your observations as supportive evidence.
    Was your device able to balance a cup suspended in the air?  Why or why not?  What were the adjustments you made to your procedures, and why did you decide to make those changes?  How did you decide the placements of the three cups and three knives or wooden popsicle sticks?  What were possible errors in this experiment?