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The Effect of Projectile Weight vs.
Distance Traveled
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Researched by Avery M.
2005-06
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PURPOSE
The purpose of this experiment was to determine how the mass of a
projectile would affect distance traveled.
I became interested in this idea when I saw a man using a trebuchet to
launch cars and pianos, and I wondered how far I could launch something
out of a catapult.
The information gained from this experiment could be useful to the
army, hunters, sport players, etc. The information would be useful to
anybody who is involved in propelling a projectile far distances.
HYPOTHESIS
My original hypothesis was that the projectile will go the farthest
with the smallest amount of weight.
I based my hypothesis on an article I read on the website
http://www.qrg.northwestern.edu/projects/vss/docs/space-environment/1-what-is-gravity.html
“The more massive something is, the more of a gravitational pull it
exerts.” So the more mass something has the more gravity will pull down
on it.
EXPERIMENT
DESIGN
The constants in this study were:
• Trebuchet catapult
• Angle of catapult
• Location for launch
• String used to launch washers
The manipulated variable was the mass of the projectile.
The responding variable was the distance the catapult shot the
projectile.
To measure the responding variable, I used a metric tape measure.
MATERIALS
QUANTITY ITEM
DESCRIPTION
1 Trebuchet Catapult
3 1/2 in. washers
1 Metric tape measure
1 22.86cm string
PROCEDURES
1. Gather trebuchet catapult parts and all of the
materials.
2. Assemble trebuchet catapult.
3. Set up catapult on flat ground.
4. Load the catapult with one of the washers.
5. Launch the projectile.
6. Measure how far the projectile was launched with a
metric tape measure.
7. Record the information.
8. Repeat steps 4-7 nine more times using the same
weight projectile.
9. Repeat steps 4-8 with a different weight washer
and then another after that.
RESULTS
The original purpose of this experiment was to determine how the mass
of a projectile would affect distance traveled.
The results of the experiment were that adding more and more weight
each time reduced the distance the washers traveled by about half of
the trial before.
See the table and graph below.
CONCLUSION
My original hypothesis was that the projectile will go the farthest
with the smallest amount of weight.
The results indicate that this hypothesis should be accepted because
the 16.4-gram weight, the lightest used, flew the farthest.
After thinking about the results of this experiment, I wonder if the
length of string that is used to hold the projectile would matter when
the projectile is fired.
If I were to conduct this project again I would do a similar experiment
but with many more trials and a bigger catapult.
RESEARCH REPORT
Introduction:
Catapults were one of the first field weapons used during the time of
the Greeks. The word “catapult” in Greek means “shield piercer”. The
trebuchet catapult is thought to have been originated in 300 BC. China.
Its use in Western Europe can be traced to the Crusades of the 12th
century.
Momentum:
can be defined as “mass in motion.” All objects have mass so if an
object is moving then it has momentum or “mass in motion.” The amount
of momentum an object has depends on two variables: how much the object
weighs, and how fast the object is moving. Momentum depends on the
variables of mass and velocity. In terms of an equation the momentum of
an object is equal to the mass of the object times the velocity of the
object. Momentum=mass*velocity. A projectile has more momentum if it
has more velocity or mass.
Inertia:
Newton:
Newton’s first law of motion says that “an object at rest tends to stay
at rest and an object in motion tends to stay in motion with the same
speed and in the same direction unless acted upon by an unbalanced
force.” Objects tend to keep on doing what they’re doing. In fact
it is the natural tendency of objects to resist changes in their state
of motion. This tendency to resist changes in their state of motion is
described as inertia.
Galileo:
Galileo reasoned that moving objects eventually stop because of a force
called friction. In the experiments using a pair of inclined planes
facing each other, Galileo observed that a ball will roll down one
plane and up the other plane always less than the original height.
Galileo said that any difference between initial and final heights was
due to friction. Galileo guessed that if friction could be entirely
eliminated, then the ball would reach exactly the same height.
Ballistics:
Ballistics is a branch of engineering that deals with motion and
behavior of projectiles like bullets, rockets, bombs, and guided
missiles.
Exterior
ballistics: Exterior ballistics deals with the flight of a
projectile after it leaves the object. One major effect on its flight
is the pull of gravity which makes the projectile fly on an
approximately parabolic path. Another effect is the drag on the
projectile by the surrounding air. If the projectile is not spinning,
or if it tumbles, it will fly a shorter distance with less accuracy. If
its flight is more level the projectile usually will achieve greater
range and better accuracy. Over long distances the spinning of earth on
its axis influences the flight path of a projectile. The flight path
also curves slightly to the right in the Northern Hemisphere and
slightly to the left in the Southern Hemisphere. In addition, because
the earth is not a perfect sphere, the slight change in gravitational
field has some small effects on the flight path over very long
distances. These geoballistic effects are especially important with
long-range guided missiles and spacecraft.
Summary:
All of these subjects really matter. If we did not know how all the
forces would affect a projectile then we could not predict how far or
fast, to shoot something as simple as a projectile from a catapult. We
would also not be able to shoot something as complicated as a missile.
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BIBLIOGRAPHY
Henderson, Tom. “Momentum” The Impulse Change Theorem November 3, 2005
<http://www.glenbrook.k12.il.us>
Henderson, Tom. “Inertia” Newton’s Laws of Motion November 3, 2005
<http://www.glenbrook.k12.il.us>
“Inner Ballistics” Ballistics October 21, 2005 http://elibrary.com
“Introduce Scientific Principle” The Bicarbonate Cannon November 1,
2005 <www.caosclub.org/members/chem11.html>
Temperley, Judith. “Ballistics” World Book Encyclopedia. 2002: 56.
“What is gravity?” Space environment February 6, 2005
http://www.qrg.northwestern.edu/projects/vss/docs/space-environment/1-what-is-gravity.html
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ACKNOWLEDGEMENTS
I would like to thank the following people for helping make my project
possible:
• My parents for helping me with getting all my materials and
helping me conduct my experiment.
• Mr. Newkirk for taking time to help me with my whole project.
• Mrs. Viernes for helping me with my project.
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