Atwood’s Machine Lab

Introduction

In this lab you will use at Atwood’s Machine to explore Newton’s Second Law. Mr. Atwood designed this machine to measure g.

• pulley
• about 1 - 2 m of string
• stopwatch
• several large paperclips
• physics classroom masses

Procedure

The following conditions must be met in each set-up that you use:

• m₂ – m₁ ≤ 10 g
• 200 g ≤ Σm ≤ 250 g

Set up an Atwood’s Machine using four different combinations of masses. Make sure to abide by the restrictions given above. For each setup calculate the theoretical acceleration. Show the free body diagram (that is, the force arrows) on each mass. Do this in your lab notebook as a first draft for what you will hand in.

For each Atwood’s Machine setup measure the actual acceleration. Design your own procedure to accomplish this.

Analysis

1. Create a neat data table to contain all of the information you will need to perform the following analysis. Show results in the same data table.
2. Compute theoretical accelerations for each setup you used.
3. Compare the theoretical acceleration to the acceleration you measured. Calculate a percent error for each setup.
4. Explain any discrepancy between the experimental acceleration and the theoretical acceleration. Do not draw on ‘human error‘ to do this but instead discuss physical limitations of the equipment/techniques used to make the measurement. Also, you may refer to assumptions made, such as that the pulley is frictionless or has no mass.
5. Above and beyond: Show algebraically how this experiment could be used to make an estimate of g, the acceleration due to Earth’s gravity. Use your method to find g for each setup for which you measured the acceleration. Explain any discrepancy between the value that you find and the correct value of 9.8 m/s². Abide by the restrictions outlined above regarding how to address experimental error.

To Hand In

Hand in your data table, calculations (with diagrams), and the results of the analysis requested above. Do this by hand or on a computer but neatness counts. Show units and show all work for calculations and use a step-by-step approach.