Studio Session 2


Open a Microsoft Word document to keep a log of your experimental procedures and your results.  This log will form the basis of your studio session report.  Address the points highlighted in blue.  Answer all questions.


Use an on-line simulation from the University of Colorado PhET group to explore vector addition.
Click HERE to open the simulation.

Explore the interface

Use the simulation to solve the following problems:

(a)  You walk 30 m in a direction 30o North of East.
Use the simulation to represent your displacement vector.

(b) To get to a restaurant, you leave home and drive 6 miles South and then 10 miles West.
Use the simulation to represent your displacement vector.

(c) Suppose you and a friend are test driving a new car.  You drive out of the car dealership and go 10 miles East, and then 8 miles South.  Then, your friend drives 8 miles West, and 6 miles North.

(d)  An airplane is flying North with a velocity of 200 m/s. A strong wind is blowing East at 50 m/s.

Understanding Motion – Distance and Time

imageEven a simple human motion such as walking is complicated.  Different parts of the human body change their position at different rates.  Their instantaneous velocities differ in magnitude as well as direction.  Today we will simplify.  We will study walking while treating the body as one rigid object.  We will plot how its position changes when it moves in front of a motion sensor.

imageYou will use the motion sensor connected to the Pasco 850 interface to collect the data.  You will measure your distance from the sensor as a function of time as you walk toward and away from the sensor.  The motion sensor is a sonar ranging device.  It uses pulses of ultrasound that reflect from an object to determine the position of the object.  Our motion sensor cannot accurately measure distances smaller than approximately 20 cm.

Equipment needed:

How does the motion sensor work?

An electrostatic transducer in the face of the Motion Sensor transmits a burst of 16 ultrasonic pulses with a frequency of about 49 kHz.  The ultrasonic pulses reflect off a target and return to the face of the sensor.  The target indicator flashes when the transducer detects an echo.

The sensor measures the time between the trigger rising edge and the echo rising edge. It uses this time and the speed of sound to calculate the distance to the object. To determine velocity, it used consecutive position measurements to calculate the rate of change of position. Similarly, determines acceleration by using consecutive velocity measurements.

Note:  The motion sensor must face the target.

Setting up the motion sensor

To become familiar with the Capstone tools, do the following exercises, and summarize your result or conclusion and your evidence for the conclusion for each exercise in your log.

image Exploration

Describe the graphs.  Elaborate on the differences between the graphs when walking at different speeds and when towards or away from the sensor.

Experiment 1

Click "Delete all Data Runs".  Open a new page.
Measure the distance from the sensor as a function of time as you walk toward and away from the sensor.  Try to move in such a way, as to produce a plot of position versus time, which matches an existing plot. 

Right click on the link motion.txt and safe the file as motion.txt in the Documents folder.

Data Analysis:

Once the graph has been successfully matched, complete the following:

Experiment 2

Try to produce one of the position versus time plots shown in the figure below.  (your reproduction does not have to be perfect, just close.)  Also record the corresponding velocity versus time plots.


Experiment 3

Use the motion sensor to study your natural walking gait.

Have one person start at least five steps away from the motion sensor.  He/she should walk towards the sensor as naturally as he/she can, stop for an instant, and walk backward away from the sensor.  Look at the position and velocity versus time data for the walk.  Repeat the experiment if necessary.  When you are satisfied with the data, adjust the graph axes to best display the data.  Copy the graph to your log and give it a meaningful name.

Use the graphed walking data to answer the following questions in your log.

Convert your log into a session report, certify with you signature that you have actively participated, and hand it to your instructor.