Physics 1050 Experiment 3. Force and Acceleration

Transcription

1 Force and Acceleration

2 Prelab uestions! These questions need to be completed before entering the lab. Please show all workings. Prelab 1: Draw the free body diagram for the cart on an inclined plane. Break the weight vector into components. Prelab 2: Does the acceleration of the cart depend on mass? Explain.

3 Contents I. Introduction II. Apparatus and Setup III. Experiment IV. Analysis V. Summary and Conclusion

4 Part I: Introduction In this experiment, you will measure the acceleration of an object moving down an inclined plane. You will analyze your data to determine the value of the acceleration due to gravity.

5 Part I: Introduction Newton s Second Law y The free body diagram of an object rolling down an inclined plane is shown at right. Newton s second law may be applied in the x-direction to obtain an expression for the acceleration. θ N mg x f

6 Part II: Apparatus and Setup Apparatus You have been provided with digital inclinometer motion sensor cart track rods clamp card

7 Part II: Apparatus and Setup Setup Plug the motion sensor into DIG SONIC 1 of the LabPro. Place the support on a rod screwed into the desktop. Screw the support into the opposite side of the track at approximately 120 cm. Place the motion sensor at the top of the track. Raise one end of the track as high as it will go. Tape the white card onto the cart and lay it on the track. (Be sure that the card faces the motion sensor.) Photo of complete setup is on the next slide.

8 Part II: Apparatus and Setup Setup

9 Part III: Experiment Launching Logger Pro Click on the icon to open Logger Pro CLICK HERE CLICK HERE Logger Pro will open with two graphs: position vs time and velocity vs time

10 Part III: Experiment Data collection LW LW Lay the digital inclinometer on the track and read the angle. Record the angle q in Table 1 of your Laboratory Workbook. Calculate and record sin q in Table 1.

11 Part III: Check your setup Hold the cart on the track near the top about 15 cm from the motion sensor.

12 Part III: Experiment Data collection Hit COLLECT in LoggerPro. Once the motion sensor makes a clicking noise, release the cart gently.! Be sure to catch it before it hits the other end! The collection will stop automatically. Examine your graphs. Do they have the expected form?

13 Part III: Experiment Data collection LW If you are happy with your data: Highlight the linear portion of the velocity vs time graph. Create a line of best fit: Click Analyze then Linear Fit. To obtain the uncertainty, double click on the box containing the slope and check the option for Show Uncertainty. Record the acceleration in Table 1 of your Lab Workbook.

14 Part III: Experiment Data collection LW Lower the track by about 2 cm. Record θ and sin θ in Table 1.! Use LoggerPro to find the acceleration and record your results. Uncertainty in acceleration is not needed in the table. Continue decreasing the angle of the track and recording the data until your table is complete.

15 Part IV: Analysis Expectations UESTION 1: Draw the free body diagram for the cart while it is on an inclined plane. Label each force clearly. Break the weight vector into components. UESTION 2: Write the equation for Newton s Second Law in the x-direction for your cart. For uestions 3 and 4, treat friction as negligible. UESTION 3: Compare the equation from the uestion 2 to the equation for a straight line graph (y = mx + b) to write the equation for the slope of a graph of acceleration vs sin q. What do you expect for the intercept? Explain.

16 Part IV: Analysis Expectations Open Graphical Analysis by clicking on the icon below. CLICK HERE CLICK HERE LW P In Graphical Analysis, enter the values of acceleration and sin q from Table 1. Create a line of best fit by clicking Analyze then Linear Fit. To obtain the uncertainty, double click on the box containing the slope and check the option for Show Uncertainty. Record your results in Table 2 of your Laboratory Workbook. Print your graph (with title and axes labels).

17 Part IV: Analysis Interpreting your results UESTION 4: Considering the value of slope and the results of uestion 3, what is the acceleration due to gravity? Be sure to include units and uncertainty. UESTION 5: Does your value of g agree with 9.81 m/s 2 within the uncertainty? If not, explain why. UESTION 6: What is the meaning of your intercept?

18 Part V: Summary UESTION 7: List at least three sources of uncertainty in this experiment. Classify them as systematic or random. UESTION 8: Write a brief summary of your experiment. Be sure to include: v the details of what was done in the experiment v how the data was analyzed v the results of the analysis v your conclusions from your experiment.

19 Wrap it up! Make sure all questions and tables of your Laboratory Workbook are complete. P Include your graph of a vs sinq.