CONQUER THAT CASTLE!
In the days of knights and ladies, catapults were used to
break down castle walls. Accuracy and strength were
important features of catapult design. You and a teammate, should you choose to work with a partner, have been
commissioned by the highest court in the land to design
and build a model catapult and enter it into the catapult
“Conquer that Castle” competition.
DUE DATE: __________ LAUNCH DATE: _________ POINTS: 35 possible
TEAMWORK: Alone or with one partner
GOAL:
Launch a large gumdrop into a 30 cm x 30 cm square, 10 meters
from launch line. The position of the first bounce determines
whether the gumdrop has hit the target or not. Catapult should be
built to survive multiple trials (about 50).
DESIGN CRITERIA:
Maximum height of device with arm at lowest position – 0.4 meters
Maximum height of arm extended upwards – 2 meters
Materials – Household supplies. Maximum cost of purchased items $5.00
NO HAZARDOUS MATERIALS, NO RAT TRAPS, NO EXPLOSIVES
Contact the teacher if you have any questions about what materials might be
allowed. Typical materials might include spoons, string, glue, rubber bands,
Popsicle sticks, wooden dowels, mouse traps, hangars, etc.
Throwing Action - The throwing action must be the free action of your device. In
other words, you may use human power to set and release the device, but you
cannot hold the propulsion arm in place once it is set nor can human power be used
to propel the gumdrop.
Orientation – There is no restriction on the orientation of the device. The
catapult can throw the gumdrop overhand, side arm, or even underhand.
Additional Design Criteria:
 On experiment day you will test your catapult on wheels and without wheels.
Lab carts may be used for the wheels.
 You will also test the catapult with and without a sling. Invent a way to
attach a sling to the end of the throwing arm.
 Last, you will test the catapult on ramps of various orientations.
Tanner, modified 2009. tannerr@thompson.k12.co.us
SCORING:
Each team will be given up to 3 throws of the gumdrop, if needed. The best of the 3 will count for
the team’s score. The team may make adjustments between throws, but the adjustment time
should be less than 1 minute. The final landing position of the gumdrop does not matter – distance
to target will be measured from the first bounce.
Scoring will be as follows:
 Up to 20 points for sketch and quality of catapult – teacher’s discretion.
 10 points for hitting the target (only one hit needed for maximum points)
9 points for missing the target but hitting within 5 cm from an outside edge.
Subtract 1 additional point for each 10 cm away from outside edge of target.
 20 points for data and calculations. Additional math points for graph if required.
 10 points for lab results (wheels, ramps, sling)
EXPERIMENTS AND FINE TUNING IN CLASS PERIOD BEFORE LAUNCH:
1. Perform 3 experiments with your launcher. Instructions will be given in class.
2. Devise a way to measure the launch angle (measured from horizontal). Measure and
record this angle on the perfected launcher (measurement can be made on launch day).
3. At home, fine-tune your launcher so the gumdrop will hit the target. Will an angle change
be enough? Do you need more power? You may use the website http://phet.colorado.edu or
make calculations to decide on the best changes.
4. Bring the perfected catapult to class the on the official launch day.
ON OFFICIAL LAUNCH DAY: Make the following measurements to use in calculations.
1. The vertical displacement of the gumdrop from release to first bounce.
2. The angle at which the gumdrop leaves the launcher.
3. The average horizontal displacement of the gumdrop (3 trials) from release
to first bounce.
4. Mass of the gumdrop.

CALCULATIONS;
Calculate the time of flight and initial velocity (hypotenuse) from y, x, ay and ax. This will involve
solving systems of equations.
Calculate the kinetic and gravitational potential energy of the gumdrop at these locations:
immediately after launch, at maximum height, and right before hitting the ground.
Calculate the momentum of the gumdrop at the same locations.
GRAPHING (use a whole sheet of graph paper):
Graph launch as instructed by your math teacher.
TURN IN
1. (20 points including quality of catapult) Sketch your catapult design and label parts with type of
materials used for each. The majority of points here are for quality of your catapult.
2. (10 points) Distance of first bounce (in cm) from outside edge of target.
3. (4 points) Neat data table showing measured values with units.
4. (16 points, 2 points each) Neat set of calculations showing equations used, substitution, and
boxed answers, labeled and with units.
5. (10 points) Lab results as requested on separate lab sheet.
Tanner, modified 2009. tannerr@thompson.k12.co.us