# ENGR101/2017 ENGR101 Organised Engineering Report

ENGR101/2017 ENGR101 Organised Engineering Report

Assignment 3

ENGR101 Organised Engineering ReportIndividual Design & Build

A model catapult

Marks: 15% of the final course grade

Due Date: Tuesday 2nd of May, 3 PM

Learning Objectives:

ENGR101 Organised Engineering Reportof this assignment are:to practice using established engineering/scientific theories in an experimental apparatus to communicate the results in a concise and organised engineering report

Relevance

It could be argued that rational design, based on sound scientific principles, is what separates professional engineers from any backyard inventor. One rather crude definition of an engineer is “a person who can do for one dollar, something that any fool can do for two”. Such a definition contains a grain of truth but, like all simplifications, it does less than justice to those engineers who find solutions to numerous non-trivial problems, such as designing supercomputers, artificial limbs, space shuttles, nuclear power plants or tall structures.

Even for relatively simple devices, we would like to think that following a rational design process will result in a superior solution to that which can be obtained by relying on trial and error or uninformed inspiration! Therefore this assignment is designed to provide you with an opportunity to put into formal practice the engineering professional skills described in lectures and workshops.

An engineer must be able not only to think creatively but to communicate clearly. A secondary function of this assignment is therefore to enable you to communicate your thoughts in a professional manner.

Assignment

Objective:

To design, build and test a model catapult that can hit the set targets. The experimental results are to be compared with the theory.

(Note: this image is for reference only. Your model catapult can be of any design or shape.)

Physics involved: Physics of catapults; projectile motion; energy conservation

Tasks to complete (see Figure. 1):

hit one target within a 0.1 m radius of a target that is 1 m away horizontally from the base of the model catapult.

hit one target within a 0.2 m radius of a target that is 2 m away horizontally from the

base of the model catapult.

You need to predict and plot the theoretical trajectory based on the parameters of your own model catapult using Excel and include the figure in your report (Section 8 – Results and Discussion). You may make any assumptions if needed, but they must be clearly stated in your report.

You will also need to use Excel to tabulate the effect of launch angle OR initial (launch) velocity on horizontal displacement.

Figure 1: A model catapult that launches a payload to hit a set target.

In your report, you need to provide a list of materials used for building your model and their costs. The total material cost of your model must not exceed NZD 20 (Recycled materials from your yellow bin are considered free). You MUST NOT purchase a commercially available catapult model.

Although your main objective is to design, build and test your catapult model, you will need to carry out rational; quantitative (with numerical results) tests first. You should carry out tests to determine how far the payload can potentially hit based on the parameters include, but not limited to, the height of the payload above the base of the catapult, the level of the catapult relative to that of the target, the weight/size/shape of the payload, the form of energy added into the system etc. Then you should test your proposed design, quantitatively if at all possible.

The engineering process taught in the lectures and the workshops may be useful when you consider the problem and work towards your final design. You should use any experience gained to show at least some degree of improvement in your design during the project.