Name ___________________________Period ___________________________

Investigation 1.1: Measuring TimeIntroduction

How do we measure and describe time? In science, it

is often important to know how things change with time.

The DataCollector allows us to make accurate, precise time

measurements by performing many different functions.

You will explore several of these functions, including the

use of a photogate.

In this investigation, you will:

time events in stopwatch mode and with a

photogate

consider how accuracy, precision, and resolution

are important to time measurements.

Materials

Part 1: Stopwatch ModeIn stopwatch mode, the DataCollector is used to measure

time intervals. The stopwatch icon indicates the DataCollector is in stopwatch mode. The clock is started

and stopped by tapping start/stop. To reset the clock, tap reset. The display shows time in seconds, and then it changes to show minutes and seconds for times longer than one minute.

1. At the DataCollector home screen, choose stopwatch mode.

2. Practice starting, stopping, and resetting the stopwatch.

3. Start and stop the stopwatch as quickly as you can. Each group member should perform 3 trials. Record in the data table below.

Member Name Trial 1 Trial 2 Trial 3

DataCollector Photogate

Name ___________________________Period ___________________________

Questions:a. What was your average start/stop time? [ HINT: Average = (Trial 1 + Trial 2 + Trial 3)/3 ]

b. Would everyone in the class have the same average start/stop time? Why or why not? Explain.

c. Could this stopwatch be used to time a marble falling from a table down to the floor? Why or why not?

Part 2: Using the Photogate1. Connect a single photogate to input A with a cord.

2. From the DataCollector home screen, choose CPO timer mode.

à There are four different functions for this mode, which are displayed at the bottom of the screen.

3. Choose interval by tapping the interval function button "I."

à A photogate icon at the top of the screen indicates a photogate is connected to the DataCollector. The word interval next to it indicates the interval function of timer mode has been selected.

4. The photogate uses a light beam to start and stop the DataCollector. Try blocking the light beam with your finger and observe what happens to the tA value on the screen.

Name ___________________________Period ___________________________

5. Which group member can get the shortest time? Each group member should perform 3 trials. Record in the data table below.

Member Name Trial 1 Trial 2 Trial 3 Average

Questions:d. How does a photogate work? Explain what has to happen in order for the timer to begin to count and

stop counting.

e. What was the shortest average time for the photogate? How does this time compare to the shortest stopwatch time (Part A)?

f. Suppose you are timing how long it takes a marble to fall from a table to the floor. Could you use the DataCollector with the photogate to find the time? Why or why not?

Part 3: Accuracy vs. PrecisionQuestions:

g. By examining the figure on the right, describe the word "accuracy" and "precision" in your own words.

Name ___________________________Period ___________________________

h. A measurement was taken three times. The correct measurements were 68.1 seconds. Circle whether the set of measurements is accurate, precise, both, or neither.

1) 78.1 s, 43.9 s, 2 s accurate precise both neither

2) 68.1 s, 68.2 s, 68.0 s accurate precise both neither

3) 98.0 s, 98.2 s, 97.9 s accurate precise both neither

A measurement is a precise value that tells how much of something there is. This is described by a number, sometimes called a quantity. But how much of what you are measuring is explained by a unit. All measurements must have units! For example, if you sit down for 5 seconds, “5” is the number, and “seconds” is the unit. If you are 6 feet tall, “6” is the number, and “feet” is the unit. YOU MUST ALWAYS INCLUDE THE UNIT IN YOUR MEASUREMENTS – a measurement is not complete without a number AND unit!

i. Fill in the table below with the correct units.

Derrick Rose weighs 190 ________________________, and his height is 6 ________________________, 3 ________________________When you finally turn 18 _______________________ old, you can buy your first lottery ticket!