SPH4U0-B Physics 12 – Portfolio and Unit Summative Design Project
Catapults and Projectiles: Medieval Weapons of Mass
Destruction
Applying Kinematics and Dynamics – Catapults and Projectile Motion
Introduction: A catapult is a mechanism used to throw missiles in ancient and medieval
warfare. At first, catapults were specifically designed to shoot spears or rocks at a
low trajectory. Later, larger catapults hurled stones, pots of boiling oil, and burning
projectiles at a high trajectory. They were used to attack or defend fortifications.
You have probably seen examples of such devices in the film the Lord of the Rings.
Catapults were widely employed in siege warfare, but with the introduction of
artillery in the 20th century, they passed from use. Today, catapults using hydraulic
pressure are employed to increase acceleration of aircraft departing from carrier
warships.
Purpose: The purpose of this lab is to determine observational and theoretical
relationships between initial velocity, trajectory angle, and launch range through the
design and construction of a lever catapult. An additional goal is to apply the
concept of stored energy in a spring/elastic launcher and draw conclusions about
applied force, acceleration, initial launch velocities, and range. The ultimate goal of
the report is to provide a thorough set of observational and theoretical data. This
data will allow the operators of the catapult to launch a small projectile to
accurately hit a target within a range between 2 and 15 m from an initial launch
position. The observed and theoretical ranges will be compared, using error
analysis, to illustrate the reliability and value of purely theoretical physics.
Components:
A. Design/Planning and Theoretical Goals – Schematic diagram, material
planning, and theoretical framework
B. Construction and Teamwork
C. Data Collection – Testing of catapult and presentation of measured data
D. Theoretical and Measurement Analysis – Theoretical values of appropriate
quantities
E. Design Accuracy – Error analysis of actual and theoretical data
F. Reflections – Post-project reflection and evaluation essay
Expectations: This project should reflect significant effort as it is a major component of
this course. More specific expectations of the project components are listed below:
A. Design/Planning and Theoretical Goals (individual): A schematic diagram of a
catapult/projectile launcher which includes multiple views (oblique, side, front or
back) of your planned apparatus. The schematic diagram must include dimensions
(or scale), construction materials, and a presentation of theoretical quantities to
meet project challenge objectives. Quantities include (but are not limited to)
initial force on the projectile, initial acceleration, time for acceleration,
initial/final velocity, range, height, time of flight, etc. Your theoretical analysis
should be comprehensive. A minimum expectation is that you would choose the
maximum and minimum range (at a sampling of trajectory angles) and solve for
all quantities listed above.
B. Construction and Teamwork (group work) – In groups of no more than 3 students
construct a apparatus that will launch a projectile at various trajectory angles to
obtain a variety of ranges within the project constraints. It is recommended that
the components to be completed by your team should be divided among the
members.
C. Data Collection (group work) – Your apparatus should be thoroughly tested at a
variety of trajectory angles and applied forces (initial velocities). Your
comprehensive dataset should be well organized and plotted for quick retrieval on
the challenge day. Your plots should represent a margin of error that you have
investigated through data collection.
D. Theoretical and Measurement Analysis at range of 10 m – Following your data
collection a comparison of theoretical values and field measurements should
examine:
a. Applied force on the projectile resulting in an initial acceleration and
initial velocity
b. Range, height, and time of flight
c. Design Accuracy – Discussion and error analysis of measured and
theoretical data, losses due to air resistance, etc.
E. Reflections – Post-project reflection and evaluation in the form of an essay will
evaluate your success and potential for improvement
Definition of Success: Design and Data Analysis
Three qualities can describe a successful project:
A. The catapult/launcher will have a range greater than 15 m
B. The catapult/launcher will have an accuracy of +/- 0.5 m within a range of 2 –
15m
C. Testing of the catapult/launcher should demonstrate consistency within trials
with identical initial conditions