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ES2D5 A2, Planar Structures and Mechanisms? Maximum length 4 pages including references, Times New Roman, Font Size 12

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ES2D5 A2, Planar Structures and Mechanisms?

Maximum length 4 pages including references, Times New Roman, Font Size 12.

Submissions to be uploaded via Tabula by

Submission deadline: Thursday Week 25 (March 24, 2022), 12:00 noon BST.

In the interests of fairness to all students, please use live sessions or Moodle forum to ask questions: I will not respond to personal requests for help with the assignment.

Your student ID is N1N2N3N4N5N6N7

Four engineers, ?, ?, ?, and ?, of body weights M? = 50+N3N4 (84 kg for ID 1234567),

M? = 50+N4N5, M?= 50+N5N6, and M? = 50+N6N7, having lost their jobs following the crash

of the automotive industry, found employment moving a pile of 20+N6 kg sacks of potato over a H = 5+N2/4 m brick wall.

To do this, engineers ?, ? and ? will construct a seesaw catapult by resting a plywood plank on a support of several sacks. They will use the catapult to toss sacks over the fence, where engineer ? will carry them away.

To manufacture the plank, the team have sourced a can of suitable epoxy and an unlimited supply of t =1+N5 mm thick veneer strips made of pine of the width of w = (10+N4)·2 cm. The

pine ultimate tensile strength is ?max=40 MPa, Young’s modulus E=9 GPa.

Design the seesaw and suggest the sack-tossing procedure.

Suggest the length L of the seesaw, its thickness a, location of the point of support x, the

support height h, and the height z of the supplementary pile of potato sacks from which the

three engineers will jump onto the seesaw. Only consider vertical velocity of sacks, leaving

the team to empirically aim the catapult across the wall.

The work should list all the assumptions made and contain all the formulae used with

references. References to somewhat reliable sources, such as lecture notes, textbooks,

handbooks, or peer-reviewed articles (if you go that far) should be in such a form that the

marker can access them. The numbers substituted to formulae must be shown so that I can

check them. Any relevant plots/illustrations are welcome.

? 3 CATS Assignment. The average student, having invested the requisite time already in self-guided study in

support of this subject, should expect to take 16 hours to complete this assignment.

Example of a formula presentation: To find the volume of a 60 kg potato sack, we assume

the density of potato at 1.08 that of water and the void fraction in the sack at 36%, so that

3

60kg 87 litres

1080kg m 0.64 p

M

V

? ?

−

= = ?

? ?

.

Precision of the above answer is at the level of

( )

2 2 2 0.10 0.04 1/ 60 10% + + ?

. For the

calculation, we have assumed that the void fraction varies up to 15% between varieties,

potato density varies by up to 4% between days after the harvest, and the precision of the

sack weight is at the level of 1 kg.

The report should contain:

Suggested L, a, x, h, z, ideally as a line of MATLAB code so that I substitute it to my script.

Description of design considerations including formulae used and assumptions made.

Marking scheme

A reasonable textbook solution of Task 1 based on consideration of energy conservation and

material strength as in lectures and past exam papers gives is expected, this gives 30%.

I will make a MATLAB script to substitute student IDs and check if the seesaw works.

If the sack scales the wall within a reasonable margin, another 20% is yours.

If the plank does not break during the toss, you get 10% more.

If ?, ? and ? do not break legs when jumping, extra 10% and thanks from ?, ? and ?.

A sanity check is required: Suggesting unreasonable parameters may reduce the mark to

below 30% depending on the gravity of the offence to the common sense.

A more detailed consideration of beam bending equations, system dynamics, and other

factors, as if you got the sack moving contract yourself, brings the mark up to 100%.

I hereby confirm that a 100% mark for the current assignment is achievable.