The Effect of Projectile Weight vs. Distance Traveled

Photo of researcher

Researched by Avery  M.


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.


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 “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.


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.



1    Trebuchet Catapult
3    1/2 in. washers
1    Metric tape measure
1    22.86cm string


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.


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.


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.


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.

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.


Henderson, Tom. “Momentum” The Impulse Change Theorem November 3, 2005 <>

Henderson, Tom. “Inertia” Newton’s Laws of Motion November 3, 2005 <>

“Inner Ballistics” Ballistics October 21, 2005

“Introduce Scientific Principle” The Bicarbonate Cannon November 1, 2005 <>

Temperley, Judith. “Ballistics” World Book Encyclopedia. 2002: 56.

“What is gravity?” Space environment February 6, 2005


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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