Translational and Rotational Equilibrium Lab
AP Physics
Background: For maintenance on large buildings, scaffolding can be hung on the outside. In
order for the scaffolding to support workers, it must be in translational and rotational
equilibrium. If two or more forces act on the scaffolding, each can produce a rotation about
either end. Therefore, either end can be referred to as a pivot point. Scaffolding with uniform
mass distribution has all of the mass concentrated at its center. In translational equilibrium the
object is not accelerating; thus, the upward and downward force are equal.
In order to achieve rotational equilibrium, the sum of all the clockwise torques must equal the
sum of all the counterclockwise torques as measured from the pivot point. That is, the net torque
must be zero. In this lab you will model scaffolding hung from two ropes using a meterstick and
spring scales, and measure the forces on the scaffolding.
Materials:
meterstick, masses, spring scales, support poles and clamps
Objectives:
 Collect and organize data about the forces acting on scaffolding
 Describe clockwise and counterclockwise torque.
 Compare and contrast translational and rotational equilibrium.
Experiment:
Construct your scaffolding as shown in the picture.
Create three different experiments using 1, 2, and 3 masses hung at different locations on the
scaffolding. Pick one of the spring scales to be your pivot point. For each experiment:
1. Draw a free-body diagram. Don’t forget the weight vector for the meterstick.
2. Label all measurements.
3. Calculate the torque for each force on your diagram.
4. Calculate the net clockwise and counterclockwise torques.
5. Find the percent difference between c and cc.
For the application section of your lab report, research and discuss two safety requirements in
our area for putting up, using, and dismantling scaffolding.