Student Features

Down You Go, H2O!
Student Section


Materials
  • Foam drinking cup
  • Catch basin (large pail or waste basket)
  • Water
  • Chair or stepladder
  • Towels
  • Toy astronaut or any plastic figure
  • Plastic jar
  • Video camera and VCR (optional)
Background Information

The person in a stationary elevator car experiences normal weight. In the car immediately to the right, weight increases slightly because of the upward acceleration. Weight decreases slightly in the next car because of the downward acceleration. No weight is measured in the last car on the right because of freefall
Earth-orbiting spacecraft experience a condition described as weightlessness. The spacecraft is in a state of free fall as it orbits. If the spacecraft has astronauts on board, the astronauts are able to move with ease because they too are in a state of free-fall. In other words, everything in their immediate world is falling together. This creates the weightless condition. The crew and contents of the spacecraft seemingly float through the air.

Image to right: This image compares how you might feel heavier or lighter than usual in an elevator. Credit: NASA

On Earth, momentary weightlessness can be achieved in a number of ways. Some amusement parks achieve a second or two of weightlessness in certain wild high-tech rides. NASA achieves about 30 seconds of weightlessness with a special airplane fondly termed the Weightless Wonder. High above Earth, the plane begins a long arc-like dive downward at a speed equal to the acceleration of a falling object. After 30 seconds, the plane pulls out of the dive and climbs back to the high altitude to begin another weightless cycle.

A falling cup, for a moment, demonstrates weightlessness. When the cup is stationary, water freely pours out of a hole in the side of the cup. If the cup falls, the water remains inside the cup for the entire fall. Even though the water remains inside, it is still attracted to Earth by gravity and ends up splashing out of the cup when it lands.


Procedures
  1. Using a pencil, punch a small hole in the side of the foam cup. Be sure the hole is near the bottom of the cup.
  2. Place your thumb over the hole and fill the cup about half full of water.
  3. Answer Question 1 on the Free Fall Worksheet.
  4. Remove your thumb from the hole. Was your prediction correct?
  5. Place your thumb over the hole and refill the cup.
  6. Answer Question 2 on the Free Fall Worksheet.
  7. Hold the cup up as high as you can (with your thumb still covering the hole) directly over the catch basin.
  8. Drop the cup into the catch basin. Carefully watch the hole to see if your predictions for Question 2 were correct.
  9. Answer the remaining questions on the Free Fall Worksheet.
A splash of water


Image to right: Be careful completing this activity, or you may get wet.
 
Group Members:_________________________________________

Free Fall Worksheet

  1. Predict what will happen if you remove your thumb from the hole in the cup.
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  2. Predict what will happen if you drop the cup with water inside. Explain your answer.
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  3. Were your predictions correct?
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  4. What happened when you dropped the cup?
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  5. Would water flow out of the hole into the cup if it were on board an orbiting spacecraft? How do you know?
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  6. Cartoon drawing of an astronaut on a spacewalk


    Image to left: Astronauts on spacewalks may not want to come back inside, because they are having so much fun.