Speed and MeasurementEngineering Challenge

Adapted from Energizing Physics Chapter 1.1-1.4 © 2011 A. Osowiecki, J. Southwick

Physics deals with the interactions between objects. In order to describe these interactions, physicists investigate the motion before and after the interaction. This activity will give you the tool of understanding constant motionby learning how to measure and describe the motion of objects.

**Reminder: You will be using the Engineering Notebook to document your solution to this engineering challenge!**

Day 1.1: Designing Devices

Goal/Objective(s): / In this activity. You will design devices you will use to measure the speed of each person in your group. This design will be constructed during the next class period.
Constraints: / When you walked through the classroom door, you walked through a wormhole that transported you back in time to before modern units (meter, seconds, etc.) of measurement were invented. Therefore, you will develop your own units of measurement.

Brainstorm:

1. Figure 1 exhibits a flow diagram of the engineering design process. Since the problem and constraints have already been identified for you, take a moment to brainstorm solutions. At this stage of the Engineering Design Process, DO NOT tries to evaluate your ideas but list all of the possibilities. To help you with this process, start by answering this question:

Q: Greg ran across the street. What info would you need to determine his speed?

1. Now that you have developed an exhaustive list, you will now go onto the next step → “Select the Best Possible Solution”.
1. For each item (distance and time), pick out your worst idea and write down an explanation for your choice.
2. Now pick out the best idea for each and write down an explanation for why they are the best.
1. Discuss the strengths and weaknesses of the devices you chose.
2. Sketch a drawing of your devices and list the materials you'll need to make them come to life.
3. Write numbered step by step procedures you anticipate using to obtain your speed data.

Practice Problem: (Use a separate sheet of paper, answer using COMPLETE SENTENCES!)

1. What are the two most important things to consider when designing a measuring device?
2. Why is it important to avoid evaluating ideas during the brainstorming process?
3. Why would someone's pulse be a poor choice for a timing device?
4. Why would “pen caps” be a poor choice for measuring distance in this activity? How about “school perimeter”? Why would that be a poor choice?

Now that you have brainstormed and chosen your devices, you will now go onto the next steps in the design cycle – constructing a prototype.

1. The next step in the design process involves constructing a prototype of the design, which engineers build before going to full production of the device. Why is it important to build a prototype before going to production?

Activity

1. Gather your materials and build your devices. In most instances, while constructing the prototypes, engineers encounter problems that force changes in the design. Record these instances in your notebook during your construction process.
1. Once you build your devices, perform a trial run of your experiment you described in Activity 1.1. Did your devices work as planned? Do you need to modify your planned procedures? If so, how?

Practice Problem: (Use a separate sheet of paper, answer using COMPLETE SENTENCES!)

1. Drawing 1.1 shows that the design process is a continuous loop. Why is it a loop? How does the continuous loop relate to your experience with this project so far?

Scientists investigate that which already is. Engineers create that which has never been.
– Albert Einstein

Day 3: Collecting Data

Now that you have your measuring devices, you will use them to measure the distance and time for each person as they run through your course.

1. In this class you are scientists and so you will need to collect three trials for each of the people in your group. Why do scientists collect multiple trials for the same experiment?
1. Prepare for recording your data by developing a table in your engineering notebook like the one below.

Variable / Units / Person 1 / Person 2 / Person 3
Trial 1 / Trial 2 / Trial 3 / Trial 1 / Trial 2 / Trial 3 / Trial 1 / Trial 2 / Trial 3
Distance
Time

Issues:

1. Gather your materials and go to the experimental area as directed by your instructor. Begin your data collection once instructed to do so, recording the data in your table. Record any issues or other observations that come up.

Note: Do not destroy or discard your measuring devices – we'll need them later!

1. What was the biggest limitation of the devices you used to collect your data?

Class Discussion:

1. Typically students find that they get different values for the three trials for each person. There are two types of error involved in making measurements -
2. Instrumental: errors caused by the measurement tool itself.
3. Operational: errors caused by the person using the measurement tool.

Describe one example of each type of error involved in your data collection, and the impact this error had on your results.

Practice Problem: (Use a separate sheet of paper, answer using COMPLETE SENTENCES!)

1. Alexia and Brian used a marble timer to measure time. They released a marble at the top of a ramp and counted one unit of time, “1 ramp” when the marble hit the ground. They split up the length of the ramp by four as shown to determine ¼, ½, and ¾ of a ramp if the marble only reached partway down.
1. Describe one instrumental error associated with this device.
2. Describe one operational error that could arise when using this timer.

Day 4: Calculating Speed

Now that you have your data, you are ready to calculate the speed of each person in your team. As you may know, speed is the distance traveled per unit time. Mathematically, you can calculate the speed using the equation shown below:

s = average speed, d = distance, Δt = time

Solving Problems in Physics
In this course, we'll use GUIDE to solve problems and perform calculations. The table to the right summarizes the steps you'll follow when doing problems all year.
You can use GUIDE both vertically (as shown to the right) or horizontally as shown in the speed example below. / Problem Solving with GUIDE
Given / Assign variables to represent the given information. Sketch the situation.
Unknown / Assign a variable to the unknown information.
Identify Tools/formula / What concepts/equations will you use to solve the problem?
Do Math / Apply the tools and solve the problem.