Coin Science: What happens to coins over time?

A new company (Coinweigh, Inc.) is trying to secure a patent for a device to revolutionize the vending machine world. Current methods for vending machines to determine which coin you dropped are mechanical or optical in nature. Both have their downsides in that counterfeit coins get through. Coinweigh, Inc. wants to market a mechanism that measures only the mass of the coin. Based on that data alone, it decides what denomination coin has been inserted.

The engineers need to know what tolerance to put on the mass measuring device. They need to know if the coins will change mass over time, and you are going to expalin to them if it does (or not) with data to back it up.

They have contracted your company (lab section) to determine what the
if coin masses change significantly over time, and if so, but what %.
You have also been asked to comment on the
procedure and make recommendations on any new methods you think might
be more effective.

Your report (15 points total) consists of the following pieces:

Procedure:
A short 3-5 sentences description of what the class did. Short and
sweet, but be complete, including what calculations you did and what
the other groups did. The reader should be able to 'reproduce' your
data using just your procedure.

Results: Put in your numbers as well as the class numbers, well labeled with some words to make it understandable.

Conclusions: Here is where you include the conclusions made by the class after all the data was crunched.

Sample Calculation:
You need to show the long drawn out (hand-written is OK) method for
calcualting standard deviation. It need to look professional, so
don't include your not-very clean work you did in lab.

You will be supplied with a large number of one kind of coin (all with dates of manufacture) your team will be 2-3 people as assigned by your instructor. Balances will be made available to you as well.

Before lab, you
must be familiar with how to calculate averages and standard deviations
(SD). Standard deviation is defined as

Here is one site with a nice description what SD is and (at the bottom) how to calculate it. Another

**Prelab
questions:** (to be completed on a separate piece of recycled
paper, handed to the instructor as you enter lab)

1. What is the average and standard deviation of the following data set: 3.4 cm, 3.7 cm, 3.2 cm, 3.9 cm, 3.1 cm, 3.4cm ? Show your work and be detailed in showing your method. Do NOT simply put the data in your calculator and give me the final result.

2. As a coins gets 'older' what do you expect to happen to the mass of the coin? There is no right/wrong answer. Defend/explain your answer.

3. Pretend for a moment you are the supervisor for all the other scientists in lab Give a short (3-5 sentence) plan of action for the day to be given to your scientists.

~MEO 9.13.07