To demonstrate how water reacts in free fall.
< 10 minutes
National Education Standards
Science as inquiry
Abilities necessary to do scientific inquiry
Motions and forces
- Foam drinking cup
- One empty and cleaned individual-size juice or milk carton
- Catch basin (large pail or waste basket)
- Chair or stepladder
- Toy astronaut or any plastic figure
- Plastic jar
- Video camera and VCR (optional)
- Student Page
- Divide the class in groups of three or four students.
- Clear a space where drop tests can be conducted. This experiment could be conducted outside to prevent messy results.
- Since students will be using water, have a mop, sponges, or paper towels available to clean up any spills.
Earth-orbiting spacecraft experience a condition described as apparent 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.
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.
Image to right: This image compares how you might feel heavier or lighter than usual in an elevator. Credit: NASA
The demonstration works best when students are asked to predict what will happen when the cup is dropped. Will the water continue to pour out the hole as the cup falls? If your school has videotape equipment, you may wish to videotape the demonstration and then use the slow motion on the playback machine to replay the action.
- Perform the following demonstration for the class.
- Stand on a ladder and drop a toy astronaut or any plastic figure. It falls to the floor.
- Next, drop a plastic jar. It also falls to the floor.
- Ask the class, "If I drop the astronaut INTO the jar at the same moment that I drop the jar, will the astronaut hit the bottom of the jar?"
- Allow students to respond.
- Demonstrate the fall with the figure and the plastic jar.
- The astronaut does not hit bottom until the jar hits the floor. Explain that the figure is in free fall.
- Discuss the situations where the students might have experienced brief encounters of free fall. Examples were given in the Background Information (roller coaster, elevator, etc.). Discuss why NASA simulates microgravity.
- Distribute the Student Pages. Read the Background Information aloud, excluding the answer section in the third paragraph.
- Divide the class into groups for the experiment. Explain that they will attempt to create weightlessness by using free fall, and they will observe how water is affected.
- Allow the groups to repeat the experiment several times.
Down You Go, H2O! Student Page
- Have each group share their observations with the class.
- Explain and review the Background Information.