Pulleys and Mechanical Advantage

Goal: To measure the mechanical advantage provided by a simple pulley.

You may need to build the equipment for this lab. Be sure to ask your parents' permission first, discuss your plans with them, and read and follow proper safety procedures for any tools you use.

Materials

Clamps, stands, or braces, and hooks for securing up to 4 pulley block-and-tackle units.
String or rope that can fit securely but slide freely over pulleys
At least two, and up to four pulleys
Spring scale graduated in grams or Newtons, accurate to 1 gram.
Weight of 10 to 30 gm

Procedure

Measure the mass of your weight.
Assemble a single pulley setup as in figure 1.

Figure 1
Using the spring scale, pull on the weight to lift it at a stead speed.
Record the force value F on the spring scale (force required to raise the mass at constant speed).
Measure the height h through which the weight was raised.
Measure the distance d through which the scale was pulled.
Record the Force F, distance d, and height h for the run.
Repeat runs for this setup at least 3 times, and average your results for ME with a single pulley.
Repeat the experiment using alternative setups such as those below (consider other ways you can combine multiple pulleys):

Data Handling

Lay out your data in tabular format, clearly noting each run and any oddities about the run.
Calculate the average value for each set of runs with the same pulley and mass conditions.
Using the relationship mechanical advantage ME = (F * d)/h, calculate the ME for each run.

Report

Your report should summarize your setup, and contain your data in tabular form, sample calclation steps, calculation results, and an analysis pointing out any trends in mechanical advantage. What are the advantages of using more pulleys? What are the disadvantages?

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