| Lab 2 of 40A| Main Menu Page| Lab 4 of 40A|

Lab 3, Atwood's Machine 01/31/2000

Courtesy of Chiung-Yuan Lin and Benli Young

Outline for Atwood's Machine experiment

Part A.

  1. Do procedure 1 & 2. Use Game Port Interface. Here total mass will be 360 grams. Let m1 = (175grams) + (5grams of a hanger) and m2 = (175grams) + (5grams of a hanger) at first. Do not forget that each mass hanger contributes an additional mass of 5 grams. See Apparatus.
  2. Print 1 Graph "Velocity vs. Time" from your existed sample data table after bad data points deleted. Indicate total mass and mass difference you used. And, find the measured acceleration a. Do not forget the method regarding the slope [M] we have learned from last two experiments.
  3. Fill out the row of "For Part A" in the given Data Table 1 at the end of this handout.
  4. Plot and print 1 Graph "a (measured) versus m2-m1" and find the value of g. I call it g A (measured) because of Slope [M] = g/(m2 + m1)

Part B.

  1. Fill out the row of "For Part B" in the given Data Table 1. Total mass here is 260.
  2. Plot and print 1 Graph "a (measured) versus m2-m1" and find the value of g. I call it g B (measured).

Part C.

  1. Fill out the row of "For Part C" in the given Data Table 1. Total mass here is 160.
  2. Plot and print 1 Graph "a (measured) versus m2-m1 " and find the value of g. I call it g C (measured).

 

The Slope of Graph "a (measured) versus m2-m1"

g(measured), Unit: (    )

%ERROR(Optional)

Part A

  

g A (measured).=

%

Part B

  

g B (measured) =

%

Part C

  

g C (measured) =

%

Hint: (3.5 points)

  • You can put three lines for Parts A, B and C in one graph. Ask for help if you like to.
  • Every slope of "a (measured) vs. m2-m1" stands 0.5 point. And every %ERROR stands 0.5 point, too.

    • Data Table 1 of your measured a

    Total Mass,

    m2 + m1,

    Unit:(  )

    Mass Difference,

    D m = m2 - m1,

    Unit:(  )

    Measured a,

    Unit: (  )

    Theoretical a,

    Unit :(  )

    %error of a

    D m

    (m2-5)

    (m1-5)

    For Part A

    360

    		 0

    175

    175

     

    		 0 N.A.

    10

    180

    170

     

     

    		 %

    20

    185

    165

     

     

    		 %

    30

    190

    160

     

     

    		 %

    40

    195

    155

     

     

    		 %

    For Part B

    260

    		 0

    125

    125

     

    		 0 N.A.

    10

    130

    120

     

     

    		 %

    20

    135

    115

     

     

    		 %

    30

    140

    110

     

     

    		 %

    40

    145

    105

     

     

    		 %

    For part C

    160

    0

    75

    75

     

    		 0 N.A.

    10

    80

    70

     

     

    		 %

    20

    85

    65

     

     

    		 %

    30

    90

    60

     

     

    		 %

    40

    95

    55

     

     

    		 %

    ?

    Part D. (3.5 points)

    Answer the following additional questions. These questions will tell you how to analyze a possible source of error, friction, and how to correct your measured results, a.

    In order to make sure that you understand the concept of Atwood's machine on page 18, let's say there is friction f between the string and the pulleys. Following the description on page 18 totally, we know that m2 > m1.
    1. Please prove that a = [(m2 - m1)/(m2 + m1)]g-[2/(m2 + m1)]f if friction f here is a constant, no more negligible. You should be able to complete this question prior to the lab period. (0.5 point)
    2. With the column of "Measured a," of Data Table 1, please give me the three positive values of "[2/(m2+m1)]f" for Part A, B, and C, respectively. Hint: What’s the value of a when m2 = m1? Requirtment: You do not need a calculator here because that any calculation here is unnecessary and forbidden!
      3. (1.5 points)
    3. Now, copy the column of "Theoretical a," from Data Table 1 to Data Table 2. With the three answers, "[2/(m2+m1)]f" for Part A, B, and C, which you have found during the previous question, please complete the 3rd and 5th column of Data Table 2.
      4. (1 point)
    4. Now, compare these two tables. Which one is more useful for any further application? Please give me quantitative arguments from these two tables to support your answer.
      5. (0.5 point)
    Remark:
    Here, you know how to find out errors caused by friction. However, there are so many sources of error, such as, the mass of the pulley, the mass of the string, air resistance, or timing precision.

    -----------Detach it, please-----------

    Suggestion

     
    Data Table 2 of your corrected a for Question 3

    Total Mass,

    m2 + m1,

    Unit:(    )

    Mass Difference,

    m2 - m1,

    Unit:(    )

    Corrected a,

    Unit: (    )

    Theoretical a,

    Unit :(    )

    %error of a

    For Part A

    360

    		 0 0 0 N.A.

    10

     

     

    		 %

    20

     

     

    		 %

    30

     

     

    		 %

    40

     

     

    		 %

    For Part B

    260

    		 0 0 0 N.A.

    10

     

     

    		 %

    20

     

     

    		 %

    30

     

     

    		 %

    40

     

     

    		 %

    For part C

    160

    		 0 0 0 N.A.

    10

     

     

    		 %

    20

     

     

    		 %

    30

     

     

    		 %

    40

     

     

    		 %

    | Lab 2 of 40A| Main Menu Page| Lab 4 of 40A|

    My Home Page

    Counter 1