2015 Assignment (25%)
Submission: Hardcopy
You may work alone or with a partner. If working with
a partner, both will be awarded the same mark.
Dr Kevin Hayward
School of Engineering
1
Assignment
Simulate the motion of a ping pong ball being launched from a lego
catapult arm.
2
You will need to complete the following:
• Calculate the projectile motion of a ping pong ball
(with drag).
• Calculate the motion of a catapult arm with a fixed
(i.e. non-pivoting) mass.
• Calculate the motion of a catapult arm with a freely
pivoting mass.
• Compare your results to a constructed lego device
(Lab 2)
• Investigate the effects of altering the following:
• Mass
• Length of arm
• Location of the arm pivot
• Launch angle
• Using previous calculation and study design a lego
arm to launch the ping pong ball as far as possible,
providing predictions of the achieved flight
distance.
Assignment
Simulate the motion of a ping pong ball being launched from a lego
catapult arm.
3
Some simplifying assumptions will be made:
• The base of the pivot is fixed (i.e. no wheels, and
enough weight to hold it down)
• Only use the weight of the control “brick”,
Investigate the effect of mass using the
calculations only.
• The launch is assumed to happen without any
breeze affecting it.
Assignment
Simulate the motion of a ping pong ball being launched from a lego
catapult arm.
4
Some things you may want to consider:
Lab 2 will be made available for you to take
measurements, you may want to determine the
following:
• Mass / Density properties of the lego
• Geometry of the lego
• Dimensions / mass of the ball
• Video footage of arm in action
• Investigate different combinations of design
parameters.
Assignment
Simulate the motion of a ping pong ball being launched from a lego
catapult arm.
5
Some things you almost certainly will need in your
report:
• Calculations of inertia
• Plots of location of important points on the arm
(i.e. COG locations) throughout the motion
• Consideration of coordinate systems
• Full working and reasoning
• Neat presentation and organisation
Other good ideas include:
• Animation of your design (this can be quite simple)
• Decent diagrams and graphs
Assignment
Simulate the motion of a ping pong ball being launched from a lego
catapult arm.
6
Some things you almost certainly will need in your
report:
• Calculations of inertia
• Plots of location of important points on the arm
(i.e. COG locations) throughout the motion
• Consideration of coordinate systems
• Full working and reasoning
• Neat presentation and organisation
Other good ideas include:
• Animation of your design (this can be quite simple)
• Decent diagrams and graphs
Hints

Break the project up into smaller more attainable steps.

Research the problem. This has been done before. But be wary
some of the solutions found online are incorrect, or over-simplified.

State your assumptions and simplifications with decent justification.

Plan your time for Lab 2

Work continuously, this is too big an assignment to do in the last
evening. A poor report will be marked accordingly

This is an engineering report. It should contain no waffle, but should
fully describe calculations so other people can verify your work (in
this case your lecturer).

This is not a simple maths problem, there is no immediate correct
answer. This is more of an optimisation problem.
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