...The Need for Speed!

Introduction to Part A

Although you may never have given it much thought to your activity the last time you walked from one place to another, you were actually observing some basic physics concepts. Motion is movement from one location to another in a certain amount of time and in a given direction In this activity you will take measurements of your motion and use those measurements to describe and determine relationships moving objects.

Preliminary Questions - To be answered individually.

Do you walk at a consistent pace, or do you speed up and slow down?

Within your group, who do you think naturally walks faster? Explain your choice.

MATERIALS

* stopwatch

* meterstick

* 2 strips of masking tape

* 5 marking blocks

PROCEDURE

Part A - Walking

Place a small strip of masking tape, labeled with your group name, on the floor in an open area where you can walk freely for at least 25 seconds.

One student will walk from strip #1 toward the end of the hallway, another will time and call out each 5 second interval. A third -student will place the marking blocks, in order, next to the walker at each 5 second interval.

Measure and record the distance and the direction from one marker to the next This is the interval DISPLACEMENT.

Repeat steps #2 and #3 for each group member.

Analysis for Part A (1-11: individual and as a class) Was the total time for each person the same? Explain why.

Calculate your total distance at the end of each five second interval. Explain how you determined the answers.

Was the total distance for each person the same ? (b) for each of your intervals the same? Explain why.

Calculate your speed during each five second interval (K-U-E-S). Do you think the average of your interval speeds will equal your average speed calculated in #5? Explain

Calculate your average speed using these interval speeds. Were you correct?

What is the independent variable? dependent variable? Explain each answer.

Construct a distance v. time graph of your walk.

Which group member had the steepest sloped line? the shallowest slope?

What specific measurement does the slope tell you about each member's walk?

Calculate the slope of your graph (K-U-E-S).

Analysis for Part A (12-14: group) Use the Graphical Analysis program to construct Distance vs. Time graph showing all group members on one graph. This graph should look like each graph you constructed in # were drawn on the same graph paper.

Determine the slope of the GA graph. Write down the values Graphical Analysis provides for your slopes. Explain any differences between your calculations above and the GA slopes.

Save your graph as…walk#, where # = class period. Your teacher needs to check your graph before you continue.

Introduction to Part B

As you now know when an object changes velocity it accelerates. In this activity you will be measuring the acceleration of a sleek, low friction car traveling down an inclined plane. In this activity you will also be using a timing device called a tape timer to explore the concept of acceleration in more detail. You will be measuring the acceleration of a car as you allow it to roll down an inclined plane at varying angles. The tape timer itself puts a small dot on a strip of paper (ticker tape). The timer makes exactly 60 dots every second, so every 3 dots represents exactly 0.05 seconds and 6 dots represents exactly 0.1 seconds. Since the times are considered exact they will not limit the certainty of your calculations. As the car moves it will pull the tape through the timer and you will be able to measure the displacement of the car’s motion by simply measuring the position of each dot. With this information you can determine the velocity and acceleration of the car’s motion. Finally you will prepare/manipulate graphs of your data to help in visualizing acceleration.

Preliminary Questions - Answer these individually.

Describe the motion of the car you expect to observe as it rolls down the ramp.

Why will the cart roll down the ramp?

Draw what you think the pattern of the dots on the ticker tape will look like?

MATERIALS 1 ticker tape timer 1 Hall’s cart data table (student made)

1 meterstick scotch tape ballast for cart

1 ~1.0 m ticker tape 1 inclined plane

PROCEDURE

Part B: Collecting the data

Check to be sure you have the necessary materials at your table. Be sure your timer has a carbon disk, if not obtain one from your instructor.

The inclined planes have been pre-set at the assigned angles.

Label one side of the ticker tape at one end - Angle = _____ and your group name.

Thread the labeled end of the ticker tape (label side down, facing the carbon disk) through the timer such that most of the ticker tape is initially draped over the upper end of the inclined plane. Attach this labeled end of the ticker tape to the back of the cart. Be sure the ticker tape has a clear path to and through the timer.

Place the car just below the timer. Turn the timer on and release the car. Be sure to catch the car before it goes flying off the table. Quickly turn the timer off to avoid needless use of the carbon disk.

Part B: Collecting the data

Check the ticker tape to be sure you have visible dots. If not, repeat steps #3 - #5, using the other side of the ticker tape, if necessary.

Remove the ticker tape from the cart.

Lay the ticker tape, flat and straight, on the lab table with label visible. Scotch tape the ticker tape to the table.

Mark the first ‘good’ dot (the “start” point) t = 0 s above the dot and x = 0 m below the dot.

Circle every 3 or 6 dots (this is labeled on your ramp) on the ticker tape. Label each data point with t = appropriate time value (each 0.05 s for every 3 dots and each 0.1 s for every 6 dots) and x = corresponding position, to the nearest 0.01 cm, from the starting point. You do not need to write the units for each data point.

Record your data (time and position) on your data table (the group will need to make one of these at this point).

Analysis for Part B

The spreadsheet will do most of the calculations for you, however, you should look at how the spreadsheet does the calculations and see if it makes sense.

Find the average acceleration over the entire time of travel. Simply average your accelerations for each interval, but leave out the following: The first two accelerations and the last acceleration.

Show/explain your calculation on the same page as your data table and label it as your average acceleration for angle _____.

Graphical interpretation of the data Sketch the relative placement of the dots on the ticker tape and explain how the dots show acceleration.

Construct a position v. time graph, with connecting lines, using the Graphical Analysis program.

Describe your graph: (a) the shape and slope, (b) what is happening to the dependent variable v. the independent variable, (c) is the graph showing constant velocity or changing velocity.

Save as...fallpos#.dat, where # = class period.

Determine the slope of your graph by using a best fit line. What does this slope measure? Record this value on your data table. Your teacher needs to check your work before you continue

Construct a velocity v. time graph, with connecting lines, using the Graphical Analysis program.

Describe your graph: (a) the shape and slope, (b) what is happening to the dependent variable v. the independent variable, (c) is the graph showing constant velocity or changing velocity.

Save as...fallvel#.dat, where # = class period.

Determine the slope of your graph by using a best fit line. What does this slope measure? Record this value on your data table. Your teacher needs to check your work before you continue

Individual Report Cover Sheet Title, name, group, group members, date, class period

Individual Work

Preliminary Questions

Part A #1-11

Conclusion Briefly and completely, discuss your answers to the preliminary questions. Basically you are re-answering the preliminary questions, only now you have experimental evidence to support your answers. Be sure to specifically mention any changed answers. Evaluation
Write an evaluation of your group’s performance during this lab activity. Specifically address each group member‘s performance of his/her specific job.(1 - 2 paragraph(s))

Write an evaluation of the lab activity itself (1 paragraph).

Please provide specific and useful information, not just, “I liked my group….this was a fun lab….”. Also, remember to include supporting evidence for your evaluation, this is a science class not a daytime talk show.