ENF 1104. Kinematics ActivityIntroduction

(V. Rouillard – 2010)

(Photographs courtesy RIT)

Preamble

Following yet another convincing win by Roger Federer at the Australian Open, his

opponent, Irma Badlouzhur, from the Peoples’ Republic of Naugudatsphort has

decided to lodge a formal protest. Badlouzhur alleges that, apart from being far

better looking, Federer used a “magic” racquet that has a coefficient of restitution

(CoR) greater than unity and therefore illegal.

ENF 1104. Kinematics Activity – Introduction (V. Rouillard – 2010)

Federer: Handsome Badlouzhur: Very ugly

Preamble (cont’d)

The Australian Tennis Federation (ATF), which is responsible for organising the

tournament, decided to deal with the protest by commissioning tests to

determine the coefficient of restitution of Federer’s racquet. This was undertaken

by an independent laboratory, Rebound Labs Inc., based in the small European

state of Lichtenstein. Unfortunately (or perhaps suspiciously), before the results

were released, the main building of Rebound Labs Inc. caught fire destroying the

test samples (Federer’s racquets) as well as most of the test data. Needless to say

allegations of ‘foul play’ and ‘suspicious circumstances’ were reported in the

popular press and other news media.

ENF 1104. Kinematics Activity – Introduction (V. Rouillard – 2010)

Preamble (cont’d)

Fortuitously, files containing high-speed video footage of two of the tests were

salvaged from the remains of the building and handed-in to the ATF by the

Lichtenstein authorities. The ATF protest committee, being past tennis players

and having little understanding of kinematics, have approached you for

assistance.

ENF 1104. Kinematics Activity – Introduction (V. Rouillard – 2010)

Video preview

Instructions on how to access the image sequences are in the hand-out)

The challenge

The ATF needs to know whether the video footage can be used to determine the

type of test carried-out on Federer’s racquet and whether accurate estimates of

the coefficient of restitution can be made from the footage. Specifically, the

following questions / issues need to be addressed and included in your report:

ENF 1104. Kinematics Activity – Introduction (V. Rouillard – 2010)

The challenge (cont’d)

ENF 1104. Kinematics Activity – Introduction (V. Rouillard – 2010)

(e) What is the coefficient of restitution between the ball and the racquet? This must be accompanied by a thorough discussion on the uncertainty of your estimates. Discuss your results in the context of rules for tennis. You also need to advise the ATF on better ways of determining the CoR of tennis request.

(a) Were the tests carried-out in free-fall or was the ball launched from a machine?

(b) If the tests were carried in free-fall, was the gravity field constant? Your response must be accompanied by a short discussion on the effects of altitude on gravitational acceleration.

(c) If the gravitational field during the tests was constant what was it?

(d) What are the variations in displacement, velocity and acceleration of the tennis ball with respect to time? This must be accompanied by a discussion on how these relate to theory.

Deliverables and assessmentTeam Preparatory task (compulsory) Start during session 1 , complete in own time (team work) , hand0in to facilitator during session 2.

Technical report (6 marks)Team technical (written) report to be completed and submitted to your designated facilitator before the start of the first session of week 8. After it is assessed, you may collect you report from you facilitator along with comments and feedback on your effort.

Reflective journal (2 marks)The submission deadline for the reflective journal is the same as that of the report.

Quiz (4 marks)Duration: 50 mins. To be undertaken during the last hour of the last session. The quiz is a closed-book session and is to be attempted by each student individually (no team work allowed) – examination conditions will apply.

ENF 1104. Kinematics Activity – Introduction (V. Rouillard – 2010)

Schedule of activities

ENF 1104. Kinematics Activity – Introduction (V. Rouillard – 2010)W

eek

6

Lecture Introductory lecture on kinematics. Important information regarding the video footage will also be given during this session.

Session 1 Familiarisation session. Start to work on Team Preparatory Task and brain-storm your team’s approach to tackling the challenge.

Own time Complete team preparatory task. Session 2 Review team preparatory task and further brain-storm your team’s approach to

tackling the challenge. Own time Work as a team to analyse both files containing high-speed video footage.

Wee

k 7

Lecture Attend lecture on applications of kinematics. Session 1 Present your results and preliminary analysis, undertake further analysis, start

working on report. Own time Prepare your report Session 2 Present draft of report to facilitator and obtain feedback. Quiz.