11.3 Indirect Measurement

11.3 Indirect Measurement Investigation 1: Sighting the height of a light pole.

In this investigation we are going to attempt to measure the height of a light pole outside by sighting.

Instructions: 1. Read all of these instructions and then attempt to draw a picture of what the situation will look like in the space underneath instruction #5. 2.Designate one person in your group as the sighter, one person as the stander, and one person as the measurer. 2. The sighter picks a point away from the light-pole and lays down on the grass with their head on the ground (getting their eye as close to the ground as they can). Then cover up the eye that is furthest from the ground. Finally, they sight the top of the light-pole with their uncovered eye. 3. The stander then moves in directly between the sighter and the light-pole. The sighter will then tell the stander to move forward or backwards so that the very top of their head directly lines up with the top of the light-pole. This process will take time as the sighter will have to tell the stander to move forward or backwards to get the top of the head perfectly aligned with the top of the light-pole. The stander must stand straight up and very still and not lean forwards or backwards in an attempt to get their head lined up. 4. The Measurer then measures the distance on the ground from where the sighter’s eye is to the middle of the stander’s feet. And then the distance from the sighter’s eye to the center of the light-pole. (Do all measurements to in meters to the nearest centimeter/hundredth of a meter.) 5. Record the measurements on the your picture below and then calculate the height of the light- pole. Show work below.

Height of light pole = ______

Average height for entire class = ______

Distance our group was from the average = ______Investigation 2 Height of Wall in Classroom

Instructions: 1. Read all of the direction and then draw a picture of the situation in the space underneath the final direction. 2. Pick one person to be the sighter, one person to be the measurer, and one person to be the recorder. 2. Have the sighter stand back from the mirror that is on the floor and move forward or backwards so that the line on the mirror coincides (lines up with) the intersection of the wall and the ceiling. Make sure you are standing straight up and not leaning forwards or backwards. 3. Have the measurer measure the distance from the line on the mirror to the point on the floor that would be directly below the sighter’s eyes, the distance from the floor up to the center of sighter’s eyes, and finally, the distance from the line on the mirror to the front wall. 4. Have the recorder record the measurements on the picture drawn on their sheet. 5. Return to your seats and copy the recorder’s measurements and use your picture to figure out how tall the wall is. Show work below.

Calculated height of the wall: ______

Actual height of the wall (given by teacher after every group is done): ______

Error (absolute value of difference between calculated height and actual height) ______