### Recent Question/Assignment

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