Static Equilibrium – Lab Activity
Experiment – Set Up
Diagram 1 – Set Up
Materials:
Each group of students will need the following items:
Three clamp pulleys
2 mass sets
White board
3 lengths of string (0.5 to 1.5m)
Light-weight ring
Protractor
Light-weight ring
Dry erase marker
C-Clamp (optional)
Electronic balance
White board with
reference lines
few paper clips
Clamp pulley
Set up your “force table” with three clamp pulleys
attached to the edges of the table. Tie three strings (of
varying length) to a light-weight ring. Pass the free end of
each string over one of the pulleys. Tie a loop in the free
Hanging mass
end of each string. Slide a white board under your
string/ring system (clamping the white board to the table
top may be desired to prevent the board from moving).
Use a dry erase marker to establish a (reference) coordinate system on the white board. Refer to
diagram 1 to help with the set up.
Experiment
Part 1
Using the force table that was set up as described above, arrange up the pulleys and strings to replicate
the situation described in pre-lab question 2 (figure D on the pre-lab). Pay close attention to the angles.
Before suspending the hanging masses from the pulley, secure the system by placing a 1.0-kg mass on
the ring (so that it will not move during the set up).
Suspend the appropriate masses over the pulleys to replicate forces A, B, and E (see your prelab
calculations). NOTE, you may need to use paper clips in addition to the hanging masses in order to
achieve the desired mass. Record the values of the masses uses to establish forces A, B, and E. Once
the appropriate masses are suspended on the corresponding strings, remove the 1.0-kg mass from the
ring. The system should not move. Record your observations and discuss the accuracy of the
(calculated) theoretical value of the equilibrant force. If the system does move, change EITHER the
magnitude (masses) or direction (angles) of the equilibrant force until equilibrium is attained. Record
the magnitude and direction of the actual equilibrant force. Secure the system (established above) by
placing the 1.0-kg mass on the ring. Remove the hanging masses from the strings.
Part 2
With no masses suspended from the strings, place the 1-kg mass on the ring in the center of the white
board. Using your values from prelab question 3, follow the same procedure described above to set up
your masses. Once all three masses are suspended from the strings and set to the predicted angles,
remove the 1-kg mass from the ring. Record all values. If equilibrium was NOT established change
EITHER the magnitude (masses) or direction (angles) of the equilibrant force until equilibrium is
attained. Record the magnitude and direction of the actual equilibrant force. Secure the system
(established above) by placing the 1.0-kg mass on the ring. Remove the hanging masses from the strings.
Write Up:
Each group member must submit their own (NEAT) pre-lab calculations.
The group must also complete the following for EACH PART of this experiment (one per group):
 A detailed description (diagram and list of values, OR an explanation) of the set up.
 Observations
 Actual equilibrant force value (if the system was not originally in equilibrium)
You may organize this
 A percent error comparing the calculated equilibrant force and the experimental
in a data table if you
equilibrant force
wish.
 The group must also complete a discussion of the error and suggestions for
improvement.