Catapult Lab

Projectile Motion
Lab 1
Catapult Lab
Objective: To apply the laws of Physics and the equations for projectile motion to design a catapult that
can accurately launch a marshmallow and hit a designated target. To compare your hypothesis to your
experimental data and understand differences between the two.
Materials and Methods:
In this lab you will be building a catapult or trebuchet. Your catapult will need to be able to launch a
pingpong ball in the range of 3-9 feet. Your catapult must be able to launch a pingpong ball at any
angle between 0 and 90 degrees.
At the end of this lab you will be given the distance to a target. Once you have your distance to your
target, you cannot test fire the catapult. You will need to make adjustments to your catapult without
testing it. Therefore, you must design and test your catapult so that on “target” day you can make
whatever adjustments are needed. It is strongly recommended that you determine your catapults muzzle
velocity. The target will be placed the same height as your catapult.
The following materials are suggested for you to build your catapults/trebuchets:
Rubber Bands
Flat pieces of wood (like popcicle sticks)
Wood Blocks
The appearance of the catapult will not be judged, but you should pay careful attention to design
elements that affect the ability of your catapult to adjust to new distances and to maintain a reliable
muzzle velocity.
You must create a lab report for this lab. It must include the following:
1) Title Page
2) Introduction
3) Hypothesis
4) Design Plan (Procedure)
5) Experimental Data Analysis
6) Conclusion
The title page, introduction, and conclusion of the lab report should be neatly typed or written and
sections should be well marked. All answers are presented/explained in complete sentences
excluding the list of materials which may be bulleted.
The following describes the information that must be present in each section to ensure full credit:
1. Introduction:
1) The purpose of this lab
2) Key terminology
2. Design Plan:
1) A list of materials used
2) Detailed steps on how the catapult was built
3) A diagram of your catapult. The diagram should have all dimensions labeled (including units)
and should be neatly drawn. Your diagram should be drawn on plain white paper and should fill
most of a single page.
3. Hypothesis:
A diagram of the path of a projectile with an explanation of the path. A vector diagram
breaking the initial velocity (muzzle veloctiy) into the X and Y components, with the
equations to solve for the X and Y components.
Equations used to determine the range, maximum height, and “hang time” of the
marshmallow. Be sure to differentiate between the X and Y axis. Discuss the equations, why
they were used, how they were solved, etc...
4. Experimental Data Analysis:
1) Data table that includes time of flight(s), distance flown in horizontal direction, and angle of
launch. You must test at least 3 different angles using 3 replicate trials for each angle.
2) A value for the average initial velocity (muzzle velocity) of the marshmallow and an explanation
of how initial velocity of the marshmallow was determined.
3) How did changing the angle affect the characteristics of your trajectory? The initial velocity?
4) Determination of the launch angle in order to hit the target.
5. Conclusion:
Your conclusion should include an overview of your findings. Discuss why the lab was successful or
unsuccessful and describe any sources of error that might be present. Give some examples of real life
projectiles whose landing spots must be carefully predicted. Discuss possible improvements for your
Point Value for this lab:
Title Page +1pt
Introduction +2pts
Design Plan +5 pts
Theoretical Analysis +5pts
Data Analysis +5 pts
Conclusion +3 pts
-2 pts for missing the target 1st try
-1 more pt for missing the target 2nd try.
- 2 pts for title, intro and conclusion not being typed.
21 pts total