Name________________________
Period___
Date ___/___/___
7  Circular Motion Lab
Trebuchet Lab
Your Mission (should you choose to accept): By varying the length of the arm of a trebuchet be able to
hit a target at a distance of 3 meters to 10 meters
Your Materials: popsicle sticks, glue, tape, masses, paper clips, scissors, trash bag, string
This message will self-destruct in 3…2…1…
You will:
1. Time how long the projectile was in the air.
2. Find the distance the projectile traveled.
3. Find the velocity of the projectile as it is released.
4. Find the force of the trebuchet on the projectile.
5. Create a graph of the relationship between the radius of the throwing arm and the distance
travelled.
6. Use your graph to hit a specific target.
7. 2pts Extra Credit for hitting the target.
Lab Report:
 Hypothesis: 2 pt
o Predict the length of the arm to hit a specific target.
 Procedure: 3 pts
o Explain how and what you designed.
 Calculations 8 pts
o Calculate the velocity of the projectile as it is released
 Results 8 pts
o Graph the relationship between the radius or length of the throwing arm and the distance
the projectile traveled.
 Conclusion 4 pts
o Explain your results
o Give ideas for improving the experiment.
o Sources of Error
Section




Include each part of the Lab Report as
outlined above (5 points for each part)
You are able to have a trial that comes
within 20 cm of 10 meters.
Lab Report is professional and neat (Pen
or typed)
Extra Credit
Total
Points
25
3
2
2
30
One Option:
Trebuchet (Counterweight powered)
Pros:





Historically Authentic
Looks very cool
Silent
Powerful and accurate if "tuned" correctly
Doesn't wear out
Cons:



Very difficult to build-you might not get it finished
Tricky to tune so it shoots well
Slow rate of fire
Materials:











15 full popsicle sticks
5 Popsicle sticks cut in half
Three pieces of string:
3"
3" with a loop tied in the end (Tie the loop first, then measure)
12"
1X3" piece of plastic grocery bag
A 1 ½" Finishing Nail
A paperclip
Fishing weights
Hot glue
How to Build It:
• Make the base.
• Glue together six sticks in a square, "log cabin" style.
• Make the uprights
• Glue two sticks together for strength. This is your upright.
• Glue a half-stick to the side of the upright as shown below. It should stick out
about 1/16 of an inch past the upright. This is your cross-beam.
• Reinforce cross-beam with another half stick as shown below.
• Repeat previous three steps to make a second upright.
• Attach the uprights to the base.
• Glue the uprights in the middle of the thick sides, with the cross-beams
pointing in.
• There should be a space of at least 3/8" between the cross-beams.
• Using four half sticks (two on each side), make braces on each upright, forming
an upside-down "V".
• Build the Throwing Arm.
• Make the arm:
• Connect two full sticks with a half stick, as shown. This is the bottom of the arm.
• Glue a full stick into the space on the top side of the arm.
???How could changing the arm length affect the performance of the catapult?
• Get an adult to help drill two holes in the bottom of the arm, about ¼" and ¾" up from
the bottom.
• Attach the sling and the pin
• PIN: Using pliers, bend a piece of stiff but thin wire (a paperclip works perfectly) into a
sharp "J" shape.
• SLING: Cut the ends of your plastic into "V" points. Using a small dot of glue, attach a
3-3 ½ " string to one point. Attach a 3" string with a loop on the end to the other point.
• Glue the pin to the top of the arm so the top of the "J" sticks out about 1/8". Use
plenty of glue for this: It has to be on very solidly.
• While the glue on the pin is still warm, attach the end of the straight string. The sling
and the looped string should hang down freely.
• Attach the throwing arm to the base.
• Insert the nail through the upper hole in the arm.
!! You might have to really work it to get it through. BE CAREFUL NOT TO STAB
YOURSELF!
• Using plenty of glue, attach the ends of the nail to the cross-beams.
!! If your catapult breaks, it will probably be at this joint, so use plenty of glue and
make it secure!
• Attach the Weights.
• Tip your trebuchet forward so the bottom of the throwing arm is touching the
table.
• Insert your 1' string through the bottom hole on the arm.
Use the string to tie on the desired weights.
??How will changing the amount of weight affect your catapult's performance?
Are there any risks?
• Firing
• Loading and releasing
• Fold the sling in half over your projectile.
• Place sling loop over pin.
• Pull throwing arm down to the ground, with sling lying flat on ground pointed
toward base.
• Hold sling in place with one finger. Quickly remove finger to release.
• Tuning.
!!Make small adjustments, one at a time, until you achieve the desired
performance. Making huge adjustments, or several adjustments at a time, can
have unpredictable results!
• If sling doesn't fly over the top of the throwing arm, you need either more
weight or a lighter projectile.
• If loop doesn't release, you might have twisted sling strings, or your pin might
be too long, nicked, or gunked up with glue.
• If trajectory is too high (the projectile flies straight up or backwards), use pliers
to bend pin slightly forward. This will delay the release of the sling, making for a
flatter trajectory.
• If trajectory is too low (the projectile flies downward into the ground), use
pliers to bend the pin slightly backward. This will release the loop sooner, causing
a higher trajectory.
From:
Kalif, W., (Feb., 2015) How to Make a Popsicle Stick Mini Trebuchet. Retrieved from
http://www.stormthecastle.com/trebuchet/how-to-make-a-trebuchet-out-of-popsicle-sticks.htm
Option 2
Step 1:
What you need:
1. Popsicle sticks
2. Super Glue
3. Double-Sided Tape
4. Electrical Tape
5. Sharp Scissors or a Knife
6. Round Pencils (as an axle)
7. Washers
8. Any sort of counterweight. (I used coins – See step 10 on how to make a
counter weight)
9. Any sort of Projectile (I used polo :P)
10. Eye Hooks
Step 2:
Step 1:
Build the base of the trebuchet using Popsicle sticks and stick them to each other
using super glue as shown.
Step 3:
Step 2:
Fortify the base from the other side by sticking more Popsicle sticks. First line the
top and the bottom edge with a popsicle stick each. Glue them firmly and wait till
they dry. Then Do the same for the right and left sides. Repeat this layering until
you have two layers. This will give the structure a firm base.
Step 4:
Step 3:
Create a structure as shown below. Do this by using a Popsicle stick and placing
two other sticks at an angle on either side of this stick, then place another
popsicle stick over it to fortify the pillar.
Step 5:
Step 4:
Repeat Step 3 and create a similar structure. These will act as pillars or columns
to support the upper body (the axle) of the trebuchet.
Step 6:
Step 5:
First use super glue to join the pillars to the base. And let it dry for a while to
strengthen the structure.
Then use washers and place them between the two pillars. One must make sure
that the holes in the washers are big enough for the pencil to fit through. Use
another Popsicle stick to fortify the two pillars together. Use double sided tape if
necessary.
Step 7:
Step 6:
Insert the pencil through the washer hole on one side and out of the other hole.
Use electrical tape and tie it on either side of the pencil so that the pencil cannot
come out of the washer. Make sure that the tape is wounded several times
across the pencil until it makes a stack wide enough to prevent the pencil from
slipping out of any edge.
Step 8:
Step 7:
Create a structure as shown. This will act as the throwing arm of the trebuchet.
Use your scissors to add small pieces of wood from the Popsicle stick to fortify
the throwing arm. Create a small cradle like structure and attach it to one end of
the arm. This will hold your projectile. Secure it using super glue.
Then attach a popsicle stick across the two sticks fanning out so as to join them.
Punch a hole in this stick
Step 9:
Step 8:
Attach the throwing arm using super glue.
Step 9:
Attach a posicle stick across the two sticks fanning out. Punch a hole in this stick
halfway through. It will act as a counter weight carrier.
Step 10:
Step 10:
Make a counter weight by inserting heavy metal pieces/ stones (I used coins) in a
plastic zip loc bag. Close the zip loc and punch a hole on top.
Step 11:
Step 11:
Insert one end of the eye hook into the hole punched in the throwing arm, the
other side should be inserted in the hole in the ziploc bag. Place a projectile in
the box and FIRE AWAY!!
From:
Kumar, M. (Feb. 2015). How to Make a Trebuchet. Retrieved From
http://www.instructables.com/id/How-to-Make-a-Trebuchet/?ALLSTEPS