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### Lab Final Guide

Disasters, Failures and other Dangerous Things

Today’s Schedule

We cover some practice problems so you prepare for the Lab Test (6 points of your grade)

- The Test will be during the lab session of this week
- It is an individual effort
- Review all your labs (1-11)
- Bring your calculator (SD and Mean) or a laptop

This PPT is available for download at:

http://www.cs.tcu.edu/people/professors/asanchez/cite10003/quizzes.html

Practice Question #1

In lab Three we recorded the following values for the live load resistance of the 15 Warren truss bridges:

- Calculate the average and standard deviation for
- The combined data (all 15 values).
- Report the STD and the Average
- Determine the range Average-STD < value < Average+STD
- What do these results tell you about your data
- Do you need to take more data?
- Why?

x

xi

Answer Question #1- Do you need to take

more data?

- Yes because the data does not follow the simple rule that 68.2% of the individual measurements should fall the range
- Note that since we have only 15 measurements we will assume a value within 65% to 70% would be OK, for this case 10 represents 66% would be OK
- However 11 represents the 73%

avg-std < x< avg+std

Question #2

In lab Four we estimated the following predicted failures for the mouse trap for 25 runs

- X: 4/25 Ball not rolling
- Y: 6/25 Diver not working
- Z: 3/25 Swing handle failure
- Represent these values in terms of their probability of occurring
- To test these values, you run the experiment 110 more time with the following outcomes:
- X happens 27 times, Y happens 37 times and Z happens 13 times
- What do this new data tell you about the data accuracy of the predictions? Why?

Answer Question #2

To test these values, you run the experiment 110 more time with the following outcomes:

Divide 4/25 and multiply by 100

In this case simple multiply by 4

Divide each one by 110 and multiply by 100

Answer Question #2

What do this new data tell you about the data accuracy of the predictions? Why?

Divide 4/25 and multiply by 100

In this case simple multiply by 4

Prediction of X and Y were off while prediction of Z was correct.

Why? Maybe I need more practice with the game before I make the predictions

Practice Question #3

In lab Six you connected solar cells in parallel and series

- Draw a connection diagram for two batteries in series and in parallel
- Which type of connection is required to increase the voltage?
- Assuming you got the following data for voltage and current with the following resistance:

- Make a plot of power(miliWatts) versus resistance load(ohms)
- What do this new data tell you the influence of resistance when drawing power?

Answer Question #3

Series

Parallel

+

+

+

1.5 volts

_

3 volts

1.5 volts

1.5 volts

+

_

_

1.5 volts

_

Series

Which type of connection is required to increase the voltage?

Answer Question #3 P=V*I

- Use Volts and Amps to determine power in Watts and multiply by 1000 to get miliWatts

Make a plot of power(miliWatts) versus resistance load(Ohms)

Answer Question #3 P=V*I

miliWatts

Ohms

- What do this new data tell you about the influence of resistance

when drawing power? Less resistance draws more power !

Practice Question #4

In lab 9 you worked with two communications protocols

- Comment on the benefits/disadvantages of using a Collision Detection versus Polling

Practice Question #5

In lab 10 you constructed a space station

- Based on the detailed accountability of the construction log, answer the following questions:
- Which was the major drawback that force you to take so many years to complete the project?
- Weather constraint: Was it the number of launches allowed per year?
- Budget constraint: Was amount of money allocated to the project?
- Technology constraint: Was the availability of the technology a problem?
- Logistics constraint: Was it a problem in they sequence of the construction and launches made?

Discuss at least two of the many issues

Answer Question #5

- Weather constraint: Was it the Number of Launches allowed per year?
- Not really through the years we have enough opportunities to launch
- Budget constraint: Was amount of money allocated to the project?
- Yes this was a major constraint, a constants flow of money would have been the best
- Technology constraint: Was the availability of the technology a problem?
- Not really however it is unfortunate that the station may get obsolete if we do build new technology early or would be used only for a few years before it is dumped
- Logistics constraint:
- If you are not careful at following the plan you may end up buying parts you do not need yet and they will rust in the inventory yard

Practice Question #6

In lab 11 you tried to set your Lander on surface of the moon

- Based on your experience in the lab. What was the major problem to overcome the lunar gravitational pull when landing from a distance of 200 meters
- Fuel constraint: Did you run out of fuel?
- Control constraint: Was it learning to add/cut fuel properly?
- Using the following data with Newton’s Formula and assuming the G Gravitational Constant to be 0.001 compute the results for the force of gravity experienced by the Lander at different distances (for this case do not worry about the units)

- Make a plot of Force versus Distance
- What do this data tell you?

Answer Question #6

Based on your experience in the lab. What was the major problem to overcome the lunar gravitational pull when landing from a distance of 200 meters

- Fuel constraint: Did you run out of fuel?
- Not really, however you have to be careful, if you use too much fuel you may run out if if and easily crash the Lander
- Control constraint: Was it learning to add/cut fuel properly?
- Yes, because since your are at higher distance the acceleration increases and you have to avoid that by increasing the speed, yet if you are not careful you go back up also wasting fuel

Answer Question #6

Using the formula and the values we get

- Make a plot of Force versus Distance

BTW the true value for G on the Earth is:

Answer Question #6

force

distance

- What do this data tell you?
- As the distance increases the force is highly reduced so you can overcome the pull of gravity

Practice Question #7

- Discuss which the Lab was the one you liked most, based on what you learned and on how it related to the topics discussed in class
- Discuss which the Lab was the one you disliked most, based on what you learned and on how it related to the topics discussed in class

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