On a piece of paper, you can measure angles using a protractor. But how do you measure how steep a ski slope is or how high in the sky the moon is? In this activity, we will create a model of an inclinometer, a tool that measures angles like these. We'll then go onto measure the height of a tree using an iclinometer.
Requirements
For this activity, you will need:
 Paper
 Scissors
 Pushpin
 String
 Tape
 Washer
 Thread
 Cardboard tube (from an empty roll of paper towels)
How to make an inclinometer to measure angles
 Photocopy and cut out this template:

Use the pushpin to poke a hole at the dot, and then slip the string through the hole. Tape the end of the string to the back of the scale.

Tie a washer onto the other end of the string so that the washer hangs below the scale. Tape the scale to the bottom of the tube.

Cut a short slit on the top, bottom, left, and right sides at one end of the cardboard tube.

Slip the thread into the slits to form crosshairs in the tube and tape the thread in place. The inclinometer should look like this:
 Measure an angle by looking through the tube toward the object you would like to measure. When the washer stops swaying, pinch the string against the scale to hold it in place. Read the angle of the string on the scale.
Your inclinometer can help you measure how tall a tree is without climbing it. Read on to find how.
Find the Height of a Tree using an Inclinometer

Measure the angle to the top of the tree with your inclinometer. Measure how far away from the tree you are standing, as well as how high above the ground your inclinometer is when you use it.

In the table below, find the row with the angle that is closest to the angle you measured. Multiply your distance from the tree by the number in the second column of the row. (If you have a scientific calculator you can find the multiplier for your angle by entering the angle and pushing the button TAN. TAN is short for tangent.)
Angle Multiply by 20° 0.36 25° 0.47 30° 0.58 35° 0.70 40° 0.84 45° 1.00 50° 1.19 55° 1.43 60° 1.73 65° 2.14 70° 2.75 
Finally, add the height your inclinometer was above the ground to the number you calculated in step 2 to get the height of the tree.
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