Practically, of course, this ideal situation cannot be realized. It can be approximated roughly by reducing friction to a minimum and by making the mass of the cord and the pulley very small in comparison with the suspended masses.

The Procedure: Read entirely before proceeding!

  1. Hang equal amounts of masses (washers) on both sides of Atwoods Machine. Establish a “net” force equal to zero. This NOT trial #1
  2. Remove a mass from “strand #1” (about 2 washers) and place it on strand #2.
  3. Record on Data Table #1 the mass on strand #1 and the mass on Strand #2.
  4. Determine the “net” mass and the “net” force.
  5. Calculate the acceleration of the system. F = ma
  6. Calculate the tensions on each strand T = mg + ma or T = mg – ma
  7. Repeat procedure “a” through “g” for a total of five trials. At all times, the total of masses are to remain on Atwoods Machine. Do not remove the masses and leave on the lab tables. This allows the mass in F = ma to remain constant so we can compare force and acceleration.
  8. During each trial, Measure the height of m2 (the mass that falls) above the floor or table. (you may need to use two meters sticks). Record this in data table #2.
  9. Use a stopwatch to measure the time it takes to fall to the floor or table, or a point just above the floor or table. (catch the falling mass so not to break the hanger). Record this time in data table #2.
  10. Calculate the speed of the fall.

Data Table #1: Show Calculations for “a” in each trial.

Trial / Trial #1 / Trial #2 / Trial #3 / Trial #4 / Trial #5
m1
m2
“net” mass
“net” acceleration
T1
T2

Data Table #2:

Trial / Trial #1 / Trial #2 / Trial #3 / Trial #4 / Trial #5
Centimeters of the falling m2
Time of the fall for m2
Speed of the falling m2

Post lab Questions:

  1. On one piece of graph paper make a speed versus time plot for each trial. Plot speed on the vertical axis and time on the horizontal axis.
  1. The slope of a speed time graph is Velocity (speed) divided by time, which is the acceleration. Determine the slope of the graph on your speed-time graph. Label this on the graph.
  1. On a second piece of graph paper, plot a graph using the values of the “net” masses on the horizontal axis. Plot the corresponding accelerations on the vertical axis.
  1. Explain why in post lab question #3, the “net” masses can be substitute for force.
  1. Does your graph in Procedure #3 substantiate Newton’s Second Law? Explain!!

Name: ______

Period: ______Date: ______