Name Tiff

Title

Trebuchet Prac

LS Teacher Kay

Link to the SACE TASK SHEET

BEFORE CONDUCTING THE EXPERIMENT

IDENTIFYING THE
VARIABLES

Identify the independent and dependent variables and 4 factors held

constant.

HYPOTHESIS

Formulate a hypothesis - a testable prediction AE1

Get this checked off by your teacher.

Independent Variable: Length of throwing arm
Dependent Variable: The distance from the trebuchet to where the projectile first hits the ground
Four factors held constant: Length of the string (15cm), mass of the projectile (2.5G), length of the counterweight
arm (51mm) and mass of counterweight (250g).
Hypothesis: If the length of the arm is at its median, then the flight distance will be at its greatest.

AFTER THE
EXPERIMENT

RESULTS

THE REPORT IS DUE ONE WEEK FROM CONDUCTING

THE INVESTIGATION

Done?

Present the data collected in a single Data Table of results. I4

Students will present their data using a Line Graph. I4

Describe the trends and relationships as shown by your data. I4

Interpret your results with reference to science concepts. AE1

Concepts that should be explored are energy transformations, factors

that affect efficiency and how levers provide mechanical advantage.

Analyse your data by discussing the precision (scatter) of your data
and by commenting on reliability. AE1

DISCUSSION:
Analysis and
Evaluation

CONCLUSION

Compare the maximum range as calculated by the equation. Discuss the

assumptions made in deriving the equation for maximum range.

Describe the sources of possible systematic and random exp. errors.

AE1

Evaluate your procedure. Describe strengths and weaknesses of your

procedure AE2

Describe and justify three improvements you could make to the

investigation design. AE2

Write a statement in relation to your original aim and hypothesis

(supports, refutes or inconclusive). AE1

Name Tiff

GROUP WORK
EVALUATION

Title

Trebuchet Prac

LS Teacher Kay

Describe any relationship between the independent and dependent

variables established. AE1

Complete the peer assessment form below for each of your group
members, rating how they contributed via initiative, focus, and
collaboration.

Start your prac report on the next page:

Title
A trebuchet is a type of catapult which was created and used as a siege machine in the middle ages. The
aim of this practical is to find the best ratio of the throwing arm between 2 and 5, and therefore the
efficiency of energy transformations of a trebuchet. This is worked out by the measured flight distance
of the projectile, divided by the maximum theoretical flight distance multiplied by 100%. The
independent variable is the length of the throwing arm, and the dependent variable is the flight distance
of the projectile. The factors that are being held as a constant are the length of the string, the mass of
the projectile, the length of the counterweight arm and the mass of counterweight.
The hypothesis of this practical is if the length of the arm is at its median, then the flight distance will
be at its greatest.

Materials Scissors
Cardboard
Pencil
Plasticine
Ruler
Retort Stand and clamp x2
Counterweight (250g)
String
Measuring tape

Procedure
1. Create the template of the trebuchet from the diagram shown in the task sheet to a ratio of 1:5
(counterweight arm is 1 and throwing arm is 5)
2. Cut out the template of the trebuchet.
3. Mark 1cm in on both sides on both side lengths of the template and join the lines so that they run the
length of the template.
4. Fold the lines marked at right angles with the underside base is perpendicular to the surface it is
resting on.
5. Put a pencil through where the counterweight arm and the throwing arm meets and 1 cm down from the
edge of the template.
6. Place clamps either side of the pencil so that the pencil and trebuchet is suspended between the two
stands.

7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.

Name Tiff
Title Trebuchet Prac
LS Teacher Kay
Attach the counterweight to the counterweight arm of the trebuchet.
Create a slit in the centre of the edge of the throwing arm about 1 cm deep.
Mould a piece of plasticine 100 times lighter than the counterweight and tie a piece of string around it,
careful to keep the plasticine in a circular shape.
Tie a knot at the opposite end of the string to where the plasticine is.
Slide the string into the trebuchet so that the knot is touching the underside of the trebuchet.
Carefully bring the throwing arm so that the plasticine string is suspended below the trebuchet and the
counterweight is almost touching the cardboard of the trebuchet.
Quickly and safely remove hand away from trebuchet so that the counter weight swings around and the
plasticine string removes itself from the hold and goes in a forwards motion.
Repeat steps 11-13 so that 3 trials have been conducted for that length of the throwing arm.
Dismantle the trebuchet completely (minus the plasticine and the string) and shorten the throwing arm
so that it is at a ratio to the counterweight arm of 1:4, with the 1 being the counterweight arm.
Repeat steps 11-15 another 3 times, but when 15 is reached, change the ratio to 1:3.5, then 1:3 and then
finally 1:2. This should mean that the total amount of all trials completed should equate to 15.
Average out each trial by adding all three trials of one ratio of the arms lengths, and then divide by the
number of trials (3). This gives the average.

Results

Name Tiff

Title

Trebuchet Prac

LS Teacher Kay

Results
The two graphs and one table above show the results gathered from conducting the practical. The table
shows each result in a numerical way, with the length of the arm being each ratio going from the ratio
1:2 at the top to 1:5 at the bottom of the table. The column graph depicts the data in a straight and
standard format so that each result is clearly defined and outlined, where as the line graph shows a
smooth, curved line of each trial and average together on each singular line. The reason why three
different formats of data representation are being used is because this allows the eye to read each
value, see where it is in relation to other trials and averages and how the ratios work with each trial.
The two pages of equations are to find the maximum theoretical flight distance of the projectile, and to
find the energy efficiency of each flight distance of the projectile. All working out in the second page is
using the averages of each ratio, rather than every trial and the average. This allows a more rounded and
correct energy efficiency to be found.
These graph results show that the ratio that gave the highest value for its average was the 1:4 ratio.
This is shown through having the highest peak in the averages out of all of the other pieces of data. The
ratio that had the highest energy efficiency was also the ratio of 1:4. This is displayed in the second
photo, because that ratio has the highest percentage of energy efficiency in comparison to all others
worked out.

Discussion
The data collected and displayed above displays that not one trial conducted was the same as the next,
with the data being quite scattered. This then means that the data is nonlinear and makes it difficult to
pinpoint outliers in the data because the data itself is quite random and uneven. This then leads to having
averages not being accurate representations of the data due to the datas randomness and non
consistency. This is easily seen in the line graph displayed above because with each separate trial, the
line dips and rises depending on the data recorded. This is most prominent in the trials of the ratio of
1:3.5, where the line starts at 7.15,then drops to 4.6 and rises again to 6.9 to average out to 6.22. This
displays that the data collection was not at a constant standard, or the release of the trebuchet.
Given the factor that human errors are always going to occur when humans are conducting experiments,
other errors could, and are likely to have occurred. These include but are not limited to; mathematics
behind the ratios being incorrect, therefore meaning that the throwing arm is shorter, or longer than
what it should have been. This could alter the results by giving the throwing arm more ability to have a
longer arm than other ratios, giving it an advantage, or a disadvantage, depending on what the difference
in the length of the arm would do.
Another error that could have occurred is that the counterweight was not placed into the same position
every time before the launch of the projectile was completed. This would have been a likely error to
have occurred because there was no testing to make sure that each time the weight was placed in the
ready position, it was in the same position as the last time. This would mean that the counterweight arm,

Name Tiff
Title Trebuchet Prac
LS Teacher Kay
and therefore the throwing arm could have more or less momentum depending on where the
counterweight was positioned. This would have affected the results, and could be the reasoning behind
why the data is nonlinear and quite random and sporadic.
An error which could have also occurred is that the measuring device was not perpendicular to the end
surface, being a wall or had incorrect markings on the device itself. This could lead to all, or some of the
data being incorrect to an extent. If the measuring device was not perpendicular to the wall, but was
then corrected, then the measurements recorded would not be to the same measurements, making the
error change from systematic to a random error.
With these errors taken into consideration, the data displayed above is likely to be incorrect, but evenly
incorrect meaning that all data is incorrect at the same level, so that a reading is still able to be taken
into consideration. With that being said, if the errors outlined above were minimalised and reduced, then
the data would be a lot smoother and would be likely to have similar measurements for each trial, making
the average more accurate.
Some strengths to do with this practical is that the teamwork to complete the practical was without
issues and flowed well. Both members of the group were able to work independently and with initiative to
achieve the goal of completing the practical. This helped keep the practical a good environment to be in
and therefore be more likely to record the correct data.
Weaknesses in this practical would have to be that not enough attention to detail was stressed upon
sections of the practical which needed more attention i.e., the release height and place of the
counterweight. If this had been achieved, then the practical would have been better, and more so likely
to have a better representation of the data collected.
Another improvement that could have been made is that multiple trebuchets could have been made,
instead of altering the length of one single trebuchet. This would have allowed less of a chance of too
little or too much of the trebuchet to be changed when changing the ratio of the counterweight arm and
the throwing arm. If 5 separate trebuchets were used and were to size for each of the ratios, then
there would be less of a chance of incorrect arm lengths and an increased amount of ease changing
between ratios. This would also allow for testing to occur of a certain ratio after all other testings were
completed if it was believed that the data recorded was incorrect and should be recorded again.

Conclusion
In conclusion, the hypothesis of the median ratio being the ratio that allows the projectile to have the
greatest flight distance. This was disproved due to the median ratio being 1:3.5, whilst the ratio with
the recorded highest flight distance being the ratio of 1:4. This could have been because of errors
outlined above, or could be because the ratio 1:4 is the best ratio for gaining the highest flight distance.

Name Tiff

Title

Trebuchet Prac

LS Teacher Kay

Team Member 1 Name:_Gabby U_____________________

A
Initiative

Focus

Generally displays

Inconsistently

Needs to be told to

initiative.

initiative.

displays

perform tasks.

Mostly focused.

Generally focused.

Displays a high level

Mostly displays

of initiative.

Highly focused on all

initiative.

tasks.
Cooperation

Superficially

Consistently lacks

focused.

focus.

Highly effective

Mostly

Generally effective

Superficial

Minimal level of

cooperation.

effective

cooperation.

cooperation

cooperation.

cooperation.

Team Member 2 Name:______________________

A
Initiative

Focus

Generally displays

Inconsistently

Needs to be told to

initiative.

initiative.

displays

perform tasks.

Mostly focused.

Generally focused.

Displays a high level

Mostly displays

of initiative.

Highly focused on all

initiative.

tasks.
Cooperation

Superficially

Consistently lacks

focused.

focus.

Highly effective

Mostly

Generally effective

Superficial

Minimal level of

cooperation.

effective

cooperation.

cooperation

cooperation.

cooperation.

Team Member 3 Name:______________________

A
Initiative

Displays a high level

Mostly displays

of initiative.

initiative.

Generally displays

Inconsistently

Needs to be told to

initiative.

displays

perform tasks.

initiative.

Name Tiff
Focus

Title
Highly focused on all

Trebuchet Prac
Mostly focused.

Generally focused.

tasks.
Cooperation

LS Teacher Kay
Superficially

Consistently lacks

focused.

focus.

Highly effective

Mostly

Generally effective

Superficial

Minimal level of

cooperation.

effective

cooperation.

cooperation

cooperation.

cooperation.

Name Tiff

Title

Trebuchet Prac

LS Teacher Kay

SACE Rubric - Trebuchet Prac

A

PRACTICAL REPORT
I4

Obtains, records, and

Obtains, records, and

Obtains, records, and

Obtains, records, and

Attempts to record

displays findings of

displays findings of

displays findings of

displays findings of

and display some

investigations, using

investigations, using

investigations, using

investigations, using

descriptive

appropriate

appropriate conventions

generally appropriate

conventions and

information about an

conventions and

and formats mostly

conventions and formats

formats inconsistently,

investigation, with

formats accurately

accurately and

with some errors but

with occasional

limited accuracy or

and highly effectively.

effectively.

generally accurately and

accuracy and

effectiveness.

effectiveness.
Describes basic

Attempts to connect

AE

Systematically

Logically analyses data

effectively.
Analyses data and their

analyses data and

and their connections

connections with concepts,

connections between

data with concepts,

their connections with

with concepts, to

to formulate generally

some data and

formulate a

concepts, to formulate

formulate consistent

appropriate conclusions

concepts, and attempts

conclusion, and make

logical and perceptive

conclusions and mostly

and make simple

to formulate a

a prediction.

conclusions and make

relevant predictions.

predictions, with some

conclusion and make a

relevance.

simple prediction that

relevant predictions.

may be relevant.
AE

Logically evaluates

Evaluates procedures

Evaluates some

For some procedures,

Acknowledges the

procedures and

and suggests some

procedures in science and

identifies

need for

suggests a range of

appropriate

suggests some

improvements that may

improvements in one

appropriate

improvements.

improvements that are

be made.

or more procedures.

KU

improvements.
Consistently

Demonstrates some

generally appropriate.
Demonstrates knowledge

Demonstrates some

Demonstrates some

demonstrates a deep

depth and breadth of

and understanding of a

basic knowledge and

limited recognition

and broad knowledge

knowledge and

general range of scientific

partial understanding

and awareness of

and understanding of a

understanding of a

concepts.

of scientific concepts.

scientific concepts.

range of scientific

range of scientific

concepts.

concepts.

Manipulates apparatus

Manipulates apparatus

Manipulates apparatus and

Uses apparatus and

Attempts to use

and technological tools

and technological tools

technological tools

technological tools with

apparatus and

carefully and highly

carefully and mostly

generally carefully and

inconsistent care and

technological tools

effectively to

effectively to

effectively to implement

effectiveness and

with limited

implement well-

implement organised,

safe and ethical

attempts to implement

effectiveness or

organised, safe, and

safe, and ethical

investigation procedures.

safe and ethical

attention to safe or

ethical investigation

investigation

investigation

ethical investigation

procedures.
Demonstrates

procedures.
Applies mostly

Applies generally

procedures.
Attempts individual

procedures.
Shows emerging

initiative in applying

constructive and

constructive individual and

work inconsistently,

skills in individual

constructive and

focused individual and

collaborative work skills.

and contributes

and collaborative

focused individual and

collaborative work

superficially to aspects

work.

collaborative work

skills.

of collaborative work.

DURING THE PRACTICAL

I3

A3

skills.

Good Because:

Better if:

Name Tiff

GRADE

Title

Trebuchet Prac

LS Teacher Kay