The purpose of this lab is to let students become familiar with working with the Vernier LabPro and accelerated systems of bodies. Graphical data analysis, freebody diagrams and euqations dealing with Newton's 2nd Law will be used to calculate the mass of the rolling cart.

 

 

 

 

 

 

Students will work in teams of two or three. On each team, one member will manipulate and measure the cart and suspended masses, a second member will operate the LabPro, and the third member will record the data provided in the group's data chart.

 

Connect the LabPro to the computer, clamp the pulley to the far end of the table, and place the motion detector on the table a minimum of 40 cm away from the cart's release position aimed at the back of the cart.

 

 

After measuring the mass of the rolling cart, securely tie one end of the string to its front axle. Pass the string over the pulley and tie the other end of the string onto the mass 50-gram hanger.

 

During the experiment you will add 50-gram increments to the hanger and release the cart. For each trial, track the cart's motion with the motion detector and record its acceleration in the chart provided below.

 

Under the Start Menu go to Programs, Math, Logger Pro 3.1 to launch the program.

 

Logger Pro should automatically set up the graphs according to the connected sensor. With the Motion Detector properly connected, the program should display graphs of position vs time and velocity vs time. First press Collect to start timing; then release the suspended mass.

 

With the completion of each trial, highlight the "smooth section" of your velocity vs time graph which displays the acceleration of the cart across the table. Then click on Analyze, Linear Fit, to obtain the slope of your line. Record your values to three significant figures in the chart provided. Repeat each mass increment two times until you have suspended a total of 400 grams.

 

One student MUST be available to "cushion the impact" of the suspended hanger and its masses just as they are about to impact with the floor. PLEASE do NOT allow them to crash on to the floor as we do not want to bend or damage the hanger or lose any slotted masses.

 

 

 

Suspended Mass (grams)	Trial 1	Trial 2	average acceleration
50
100
150
200
250
300
350
400

 

 

 

Suspended Mass (grams)	1/M (kg-1)	1/a (sec2/m)
50
100
150
200
250
300
350
400

 

 

Open the EXCEL graph PulleySystem.xls and chart your values. After filling in all required information, save your graph as

 

LastNameLastNamePulleySystems.xls

 

 

Step 1a.  On your graph's printout, draw a freebody diagram of the rolling cart (m). Include the forces tension, weight, and normal.

 

Step 1b. On your graph's printout, draw a freebody diagram for the suspended mass (M). Include the forces tension and weight.

 

Step 2. On your graph's printout, write the equations of motion for each body - the rolling cart and the falling suspended mass

 

Step 3. We will now use data analysis techniques to determine the experimental values for the mass of the rolling cart and the acceleration due to gravity.

 

Initially solve these equations from Step 2 simultaneously for the suspended mass (M). Your solution should only involve letters - no numerical values.

 

Next rearrange this equation to match the format of the equation from your EXCEL graph where your y-axis variable is (1/a) and your x-axis variable is (1/M). Have your teacher check off your result.