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Lab 4, Newton's Second Law, Part I, 02/18/2000

Courtesy of Chiung-Yuan Lin

 Here is a sample data table in Procedure 6.

Frequent Problems on Performance
  1. While the glider passes through the 2nd photo-gate, the hanging mass should be unobstructed. Refer to Procedure 3.
  2. Refer to Procedure 3. Adjust the height of the photo-gate properly and again after preparing the inclined plane in Procedure 13.
  3. The hanging mass should be steady for each measurement. Refer to Procedure 3.
  4. After each measurement, do not slide the glider back through the photo-gates. Refer to Procedure 6.
  5. Be sure to distribute the heavy weights evenly on the glider in Procedure 8 and Procedure 11.

    6. Here is a Sample Graph "a vs. ma" in Procedure 9.

  6. For the inclined plane, remove the string and hanging mass from the glider. Then follow Procedure 13.

Additional Notices

Procedure 6

Don't press until five measurements are finished.

Here is a Sample Graph "a vs. 1/(m+ma)" in Procedure 12.

Procedure 8

We move the weights from the glider to the hanger because we like to keep m+ma fixed.

 

Procedure 13

Don't forget to adjust the photo-gate heights. If necessary, reverse the connections for gate 1 and gate 2 so that gate 1 is uphill.

The height of the metal block is h, and the distance between the track legs along the track (not along the horizontal) are D. Then the angle is, roughly, q @ sinq = (h/D) Þ g ´ sinq = g ´ (h/D)

Outline for Newton's Second Law _Part I

Courtesy of Benli Young

1. Glider length: _________________, Unit:(    )

Item

Mass, Unit:(    )

Hanger

 

Glider

 

Small Weights

　

　

　

　

Large Weights

 

 

 

 

2. Do not print out the "data tables" of measurement, which are required in procedure 6 and 7.

3. Refer to Procedure 8. Make measurement with total mass fixed.

Total mass, (m+ma) = glider + 4 small weights + hanger = _________, Unit:( )

Hanging mass ma, Unit:(    )

Measured Acceleration a with SDOM, Unit: (    )

Theoretical Acceleration mag/(m+ma), Unit: (    )

%Error (Optional)

5 (hanger’s)

　

±

  %

(5+10)

　

±

  %

(5+20)

　

±

  %

(5+30)

 

±

  %

Refer to Procedure 9. Print out a graph of "a vs. ma" and compare the slope with "g/(m+ma)".

4. Keeping ma fixed at 15 grams and varying m with the large weights gives the data.

Total mass

m+ma, Unit:(    )

Measured Acceleration

a with SDOM, Unit: (    )

Theoretical Acceleration

mag/(m+ma), Unit: (    )

%Error (Optional)

(186+15)

  

±

  %

(186+50+15)

  

±

  %

(186+100+15)

  

±

  %

(186+150+15)

  

±

  %

Question 12-1: (2 points) Refer to Procedure 12.

  • Print out a graph of "a vs. (m+ ma) -1". (1 point)
  • Compare the slope of this graph with "mag" in percentage for 0.5 point.
  • The work of finding the theoretical slope, “mag” , stands 0.5 points. The slope should be close to “mag” = (1.500´ 10-2 kg) ´ (9.80 m/s2) = 1.47´ 10-1 kg-m/s2

    •

    5. Refer to Procedure 13. Measurement of acceleration on the inclined plane:

    The thickness of metal block (h): _________________, Unit:(    )

    The distance between the supporting legs (D): _________________, Unit:(    )

    The angle of the inclined plane Θ @ sinΘ= (h/D) = _________________.

    Therefore, g = a/sinΘ or a = g ´ sinΘ = g ´ (h/D).

    Glider mass m, Unit:(    )

    Measured Acceleration a with SDOM, Unit: (    )

    Theoretical Acceleration g(h/D), Unit: (    )

    %Error (Optional)

    186

    		 　

    ±

    		  %

    (186+50)

    　

    ±

    		  %

    (186+100)

    　

    ±

    		  %

    (186+150)

     

    ±

    		  %

    Question 15-1: (2 points) Does acceleration depend on the glider mass?

    Requirement:

  • 0.5 point is for the theoretical prediction.
  • 0.5 point is for your experimental verification.
  • Print out Graph "Measured a vs. Glider mass m." (0.5 points)
  • Use [M], [B], [R], and the percent errors (0.5 points), etc., to support your argument.

    • I am a skeptical TA. I will say that according to your Data Table and Graph, maybe acceleration does depend on the glider mass like an exponential function or something. And because of that, all physics textbooks have to be re-written. How will you defend "Newton's second law"? How will you do to support the agreement between your theoretical predication and your experimental measurement?

    Question 15-2: (2 points) Does acceleration depend on what distance above the first photo-gate the glider starts? Try a few different distances.

    Requirement: Follow the given hint in Question 15-1. It is time for you to design an experiment to answer this question.

  • 0.5 points is for the theoretical prediction.
  • 0.5 points is for your experimental verification
  • You have to design your own data table for 0.5 point.
  • Print out a graph (0.5 points) to support your experimental argument.

    •

    Reminder:You should make a theoretical prediction at first. Secondly, you should present a data table and/or a graph of your experimental measurements. Then, compare and discuss your theoretical prediction and experimental result. Furthermore, discuss differences between them if they do not agree with each other. All comparisons should be quantitative and better in percentage. Each of your statements should have a reason based on a theoretical equation or a quantitative experimental calculation.

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