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Hydroponics · Magnetic Chamber · Newton's Laws· Effervescence · Chromatography · Simple Machines · Live Lesson 1 · Live Lesson 2
THE LOST
“If the sphere tumbles across here, you can still see
the lines.”
Introduction:
The
wonder of the
Background:
Before
continuing, read carefully Bob Mayfield’s discussion of the proposed
experiment. How the demonstration
evolved is, in itself, a useful learning experience teaching the principles of
The
culmination of the iterative process was a projectile experiment. Two separate balls, a billiard ball and ball
bearing are independently catapulted along identical paths. The billiard ball, having twice the mass of
the steel ball bearing and twice the diameter, would exhibit twice the
inertia. This would lend itself to
examining
As
Mayfield elaborates, the challenge, in a zero-gravity environment, is the application
of like force and direction to each ball’s mass. In order to glean some type of quantitative
data, a meter long graduated poster is affixed to the Shuttle’s locker
wall. The pair of balls must be
catapulted simultaneously in the same direction past the length of the poster. This permits comparative tracking
based on equal forces applied to projectiles, one a half the mass of the other. Below is a video capturing discussion and planning for the catapulting
of the balls (spheres) past the meter long backdrop.
Planning the Projectile Launch Path
Click on:
newton_experiment_ground_practice.wmv
to play the video.
Such
an experiment reminds educators of Galileo’s drop of two objects, a feather and
an apple, from the Learning Tower of Pizza. Of course, this is often used to confirm another of
Christa’s
lost lesson differs in that the effect of gravity on the billiard ball and
steel ball bearing is absent. Only the
mass of the objects differs, keeping the applied forces at equal
magnitudes. Solving for acceleration
yields the result: (A)cceleration (=)
equals (F)orce (/) Divided by (M)ass. Since the force applied to each projectile is equal while the mass of the ball bearing is
half that of the billiard ball, the solution has the ball bearing’s initial
acceleration twice that of the billiard ball. In order to grasp the difference,
a video must capture the catapulting of the balls past the meter long
backdrop. Obviously, the ball bearing
will quickly outdistance the billiard ball. However, beyond that, the measure of how much is the question? This has to do with the elapsed time since
the like force was applied simultaneously for the same amount of time to each ball. Again, use of video would quantify such a result.
Indeed,
without gravity, demonstrating Galileo’s experiment is not possible. However,
the stripping away of gravity offers the benefit of simplifying the
demonstration of
The
idea of eliminating gravity is addressed by Mayfield’s description of a
proposed classroom demonstration of Christa’s Lost Lesson. Since gravity acts perpendicular to the movement
of an object parallel to the earth, the
The
class experiment uses the same type projectiles, a billiard ball and a steel
ball bearing of half the mass. Additionally,a meter rule is
needed.For applying equal forces to the projectiles,
some kind of ball point pen spring mechanism is used. These items replicate Christa’s lost
lesson.To assist in quantifying the
result as well as providing identical paths and direction, v-slotted planks of wood are needed.
Of
course, a video must record the race scene. Positioning the camera on a
tripod above the pair of tracks permits later analysis. Video playback would
display the pen retractor’s snap launch of the two projectiles as well as their
comparative progress versus time along the v-grooved adjacent tracks.
Procedure:
The challenge of applying equal forces for equal times to the
projectiles was considerable. The
solution is shown above, a release of each ball using a suction system. For the zero-g aircraft practice session,
Christa provides the suction on a plastic hose which holds the ball bearing in
place until she ceases sucking on the hose with her breath. The demonstration is a rudimentary version of
the orbital version. The actual
apparatus would include a spring within the tube. Suction holds both projectiles in place and
the springs in their coiled positions. Both the billiard ball and steel ball are catapulted by the spring when
the suction is terminated. The spring force is equal for both projectiles. Cups of diameters slightly less than each of
the spheres hold them respectively in place. Their springs are depressed while
suction is applied.
Release of the suction/vacuum pressure permits the two springs
to uncoil simultaneously. Though the
author has no pictures of the apparatus, it likely was not Christa’s lungs
which would have provided the suction.
It is difficult to imagine a device like that displayed in the
video. Imagine a pair of tubes, “Y”
connected so that one orifice can be sucked on straw-like. Loading the two opposite ends with the two projectiles would require one to suck on
the straw vigorously while placing billiard ball and steel ball bearing into
their respective cups. While holding
one’s breath to keep each projectile snugly seated in its respective cup,
Christa would have had to aim each tube in the same direction. Likewise, she would be required to assure
each tube held the same position with respect to the meter long poster attached
to the shuttle locker wall. Then, with
video being recorded, she would cease sucking. This would release the projectiles under spring force. As a result, they would race across the shuttle interior. Likely, several members of the crew would be
needed to collect the billiard ball and steel ball, and, perhaps, an exhausted
Christa. Below is the video of the
simulated experiment as performed in zero-g.
Christa Sucking on Tube to Hold Steel Ball Bearing in
Place
Click below to play the video.
newtons_laws_zeroG.wmv
A Classroom Version of Christa’s
The following demonstration closely replicates
Christa’s experiment seen in the above video:
Background:
The lost Newton Laws lesson offers
students and teachers a mathematical means of demonstrating the law of
momentum, derived from
Materials:
1)
A billiard or golf ball
2)
A steel ball bearing or marble half the
weight of the billiard/golf ball
3)
Two one Meter Long V-grooved 2” by 4” building frame boards
4)
Video camera and VCR
5)
A small scale for measuring weights
6)
Two ball point pen spring assemblies
7)
A one meter long scribed poster
Steel Ball Bearing and Billiard Ball on V-grooved Tracks
Cutaway view of spring release mechanism providing equal
forces to each ball.
Process:
*1. Collect the
listed materials. Using a router with a
“V” bit, scribe the channel for the ball bearing and billiard ball in the
center of each board parallel to the boards’ lengths.
*2. Position the
boards in lengthwise contact with a yard stick, meter stick, or scribed poster
laying lengthwise on the table beside the v-slotted tracks. Have the end of the measuring media
coincident with the start of the tracks.
*3. Place each
ball in the v-groove at the start of the respective tracks. Mount the video camera overhead on a tripod
with the camera view centered on the tracks, perpendicular to the plane of the
tracks.
*4. Start the
videoing of the activity.
*5. Select two
students to release the ball point pen springs by pressing each pen’s release
button. (Note: Prior to the actual
demonstration, have the students practice snap releasing the springs. This is done to
*6. Instruct the
students how to position their pens’ retractor shafts snugly against each of
the balls, assuring the direction of the retractors’ release force is applied
through the center of mass of each ball parallel to the surface of the table
and v-groove path.
*7. Voice a launch
count down from ten, instructing the students to press the pen release buttons
at the sounding of the “ONE” count.
*8. Repeat the
process several times.
*9. Play back the recorded video of the runs on a
television using a video tape recorder. Select for analysis the run which
most closely satisfies the criteria described in step 6. above.
Analysis:
The
video offers an excellent means of analyzing the experiment. A rough confirmation of
Questions to
Answer:
1.
What did you conclude from the results of
the analysis regarding the effect of mass on the velocity of a projectile to
which a momentary force is applied?
2.
What factors might have caused the
resulting analysis to fail to confirm the law of momentum when the two
projectile velocities were compared?
3.
Read Jules Verne’s book FROM THE EARTH TO
THE MOON. How did his launch system
compare with the experiment above?
4.
Can you propose an improved means of
applying like forces to the steel and billiard balls?
5.
Without knowing the ratio between the two
projectiles, how might one determine the mass of the steel ball knowing the
mass of the billiard ball using the experiment above?
What Would Have Happened on Challenger?
This question is best answered by actually performing
the above experiment. In the process, ask these questions:
1. What added resistance exists on earth, not
present for the Challenger demonstration?
2. What danger/peril might one encounter
performing the experiment on Challenger not present on earth? Likewise, what danger/peril might one
encounter performing the experiment on earth which would not be a factor on
board Challenger?
3. Do you believe Christa would have been
successful in demonstrating
4. How would you suggest changing the proposed experiment to assure a more likely successful
outcome? Likewise, what might have
been eliminated to assure successful
results?
5. What about the filming of the
demonstration? Would it have been easier
on Challenger or on earth using the
video camera and tripod.
For
added information or copies of the project, contact the project editor Jerry
Woodfill, at ER7, NASA JSC,
The
project is a work of the Automation, Robotics, and Simulation Division of the
