The Challenge. What to Do

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Carmella Sherman
6 years ago
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1 LEGO Protractor The Challenge How can you accurately measure an angle? Create your own protractor using a rotation sensor and gears. Do this protractor activity first, then try the Slingshot or Peripheral Vision Experiment activities. This activity requires: ROBOLAB 2.0 or higher The Infrared Transmitter with serial cable #9713 RCX #9709 Team Challenge Set #9793 or #9794 A LEGO Angle Sensor #9891 (also called a Rotation Sensor) After completing this activity, try either the Slingshot or Peripheral Vision activity. What to Do Building Ideas The angle rotation sensor measures rotations to the nearest sixteenth of a rotation, which is equivalent to 22.5 degrees. To make a more precise protractor, mount an eight-tooth gear on an axle through the rotation sensor. Mesh it with a forty-tooth gear on another axle. This second axle will be attached to the bottom of the protractor arm-- the piece that rotates to measure the angle. Build a frame to hold these pieces together: the rotation sensor and small gear, the protractor arm and large gear. Programming Ideas Write a program in Programming Level 1 to control the protractor. Use a touch sensor on port 2 to signal when to log the rotation sensor. Make sure to select the rotation sensor icon rather than the angle sensor icon. Journal Import a JPEG of your protractor to a Journal page. 1

2 Conducting the Test Use your protractor to measure an angle. Upload Upload the data to the computer. Compute Use Compute Tools 1 to write a program to convert the raw data to an angle. To do this, you will need to figure out how far the big gear turns when the little gear turns onesixteenth of a rotation. (Hint: First, figure out how many times the little gear turns for every time the big gear turns.) Once you have figured out how far the big gear turns, multiply that fraction by 360 to convert it to degrees. In Compute Tools 1, multiply your raw data by this degree number. The new data set will show your angle in degrees. Journal On a new Journal page, describe how your protractor works. Include an explanation of how you converted the raw data to degrees. How accurate is your protractor? Does it measure angles correctly to the nearest degree? Five degrees? Ten degrees? Extension Use additional gears to make your protractor more precise. Hint: Try putting more than one gear on a single axle. 2

3 Teacher s Notes for LEGO Protractor LEARNING OBJECTIVES Students will understand: How to measure angles. How gear ratios work. How to use Compute Tools to perform operations on raw data. DISCUSSION Building Ideas Students use an angle sensor and gears to build a protractor. Programming Ideas The Pilot version of Investigator (Levels 1, 2, 3) includes an angle sensor icon as well as a rotation sensor icon. 3

This icon takes the rotation data, measured to the nearest sixteenth of a rotation, and converts it to degrees by multiplying by 22.5.

4 This icon takes the rotation data, measured to the nearest sixteenth of a rotation, and converts it to degrees by multiplying by You may wish to introduce this activity by having students experiment with the built-in angle sensor and discover its limitations for themselves. Here is a solution using Program Level 1 using the rotation sensor icon. The protractor described in the student handout meshes a forty-tooth gear on the protractor arm with an eight-tooth gear on the rotation sensor. So, for every one-sixteenth of a rotation that the small gear makes, the large gear makes one-eightieth of a rotation. Multiplying 360 by one-eightieth gives 4.5, so each sixteenth of a rotation measured by the rotation sensor is equivalent to 4.5 degrees. 4

Extension Students can add additional gears to their protractors to make them more precise.

5 The first image below shows the raw data for an angle displayed in the View Area. The second image shows the data converted to an angle in degrees using Compute Tools 1. Extension Students can add additional gears to their protractors to make them more precise. For example, place an eight-tooth gear on the same axle as the forty-tooth gear in the original design. Mesh this eight-tooth gear with a second forty-tooth gear on another axle, which attached to the protractor arm. For every sixteenth of a rotation measured by the rotation sensor, the protractor arm moves degrees. 5

Here Comes the Sun. The Challenge

Here Comes the Sun. The Challenge Here Comes the Sun This activity requires ROBOLAB 2.0 or higher, the Infrared Transmitter and cable #9713, RCX #9709, elab sets #9680 and #9681. The Challenge Invent a car that finds the optimal light