Purpose: To balance the torque applied on a beam.
Simulation Used: Balancing Act from the PhET collection at the University of Colorado.
When a force F is applied at a distance r from an axis, and the angle between the two is given as θ, the torque is defined as:
By convention, the counterclockwise (CCW) torque is considered positive and the clockwise (CW) torque is considered negative.
When an object is at equilibrium, both the net force and torque must be zero:
In other words, the CCW torque and CW torque must be equal in absolute value.
- Preliminary Settings.
- Open the simulation Balancing Act.
- Select "Balance Lab" tab from the top
- In the "Show" window to the right of the simulation, select "Mass Labels", "Ruler", and "Forces from Objects".
- Activity 1: Two Bricks
- From the brick window, click and drag one 20-kg brick (Brick 1) at 1.0 m to the left of the pivot point (location x1 = -1.0 m)
- Find the location x2 of a second brick (Brick 2) in order for the beam to be balnced. You can check whether the beam is balanced by clicking on the "Remove Supports" button at the bottom.
- Calculate the corresponding torques, Torque 1 and Torque 2.
- Repeat for all the selected bricks and locations given in the table below. Record the location of Brick 2 with its correct sign: "plus" for locations to the right, and "minus" for locations to the left of the pivot point.
- Data and Results: Record your results in the table below. Follow the example (row 1)
- Activity 2: Three And More Bricks.
- Click and drag two bricks to the locations given in the table below. Determine the location of a third brick so that the beam is balanced.
- Calculate the corresponding torques, as well as the net clockwise and counterclockwise Torque.
- Data and Results: Record your results in the table below following the example done in row 1.
- Activity 3: Determine the mass of an object
- In the Bricks window, use the right and left arrows to navigate to the mystery objects: A, B, C, and D.
- Place object A on the beam, balance the beam by placing bricks or humans. Determine the mass of A in kg.
- Repeat for objects B, C, and D.
- Data and Results: Record your results in the following table.
- The Java Applet comes from the PhET Interactive Simulations at the University of Colorado, Boulder.
- Some activities are based on the "Laboratory Manual, Physics 231 - 232" by Walter Wimbush, Northern Virginia Community College, 2008.
Created: Sat Jul 07 14:32:17 Eastern Daylight Time 2012
Last modified: Sun Jul 8 23:06:58 EDT 2012