# Move a Wall

## Purpose:

Our everyday world seems pretty sturdy. Floors are solid, walls remained fixed, and we donâ€™t seem to do much to these solid features as we go about our daily lives. But when we look at the world from a different scale, the scale of the nanometer, these solid features are anything but stationary. In this activity, students use math to determine just how much they move a wall when they lean against it.

If you have any questions about this lab, please contact Joe Muskin at (217) 265-6481 or by email at jmuskin@uiuc.edu.

## Materials:

 Tripod Laser level ½" diameter × 3' solid steel rod T-pin T-pin with small mirror attached Roll of double sided carpet tape Tape measure Scissors Sturdy table Click on the image above to open a full sized version.

## Experimental Procedure

1. Prepare objects:
 Place the table near the solid wall, approximately six inches from the wall. Add weight to top of table. Cut a square of carpet tape that is between 1.5 and 2 cm per side. Center and press the sticky side of the tape on the end of the long metal rod. Remove the paper backing of the tape and push the sides of the tape down around the rod.
2. Set and align bar:
 Rest the rod on the two T-pins, one of which is attached to a mirror. Be sure the rod is not touching the table. Roll the rod on the T-Pins towards the wall. Push the rod firmly against the wall so that the carpet tape adheres to the wall. Place laser level on tripod. Adjust the height and position of the tripod until the laser dot is shining into the middle of the mirror. Carefully adjust and tilt the mirror on the T-pin until the reflection of the laser dot can be seen on the opposite wall. The reflected laser dot should be higher than the height of the mirror.
3. Push wall:
 Mark the initial point of the reflected laser dot on the opposite wall. Have a volunteer push the wall near the table where the rod is attached. Mark highest point the laser points on the opposite wall.
4. Take measurements:
 Measure the four key distances. Record the measurements on the activity worksheet. Do the Math!

• Activity Guide

Instructors guide containing all relevant information to conduct the lab.

• Presentation

Presentation for teacher to introduce the activity to students.

• Worksheet

A worksheet to be completed by students.

## Safety:

Lasers should not be directed at the face. Laser light can cause vision impairments.

## Acknowledgements:

Thanks to Scott Maclaren for technical information and the use of his wonderful AFM images. And thanks to Michael Condren for demonstrating that someone could observe the effect of a person pushing on a wall.

## Developers:

Adam Poetzel, Matt Hopkins, Matt Ragusa, and Joe Muskin