## Tuesday, September 15, 2015

### Measuring time...

Today we started by splitting everyone into permanent pairs and assigning each pair a particular robot.  Our goal was to figure out how far the robot moves per rotation of each wheel so that we can predict where the robot will end up as we program it to go places.  We used three different methods to find out this information.  First, we used the formula for the perimeter of a circle (P):

P = π * D

where:

π = 3.14159

and D is the wheel’s diameter (diameter is a straight imaginary line that passes through the center of the circle and cuts it in half).   So each pair got a tape measure and proceeded to measure the diameter of the wheel.  Almost everyone arrived at 1 5/8 inches for the diameter of the robot wheels.  Which created the following issue.  How do we convert 1 5/8 inches to a decimal value that we can plug into a calculator?  So we explained that to do this, we did the following:

5 ÷ 8 + 1 = 1.625 inches

and when we plug this value into the perimeter equation we get:

P = 3.14159 * 1.625 = 5.1 inches

Next, we asked everyone to program their robots to turn both wheels 1 rotation and asked them to measure how far the robot moved.  Almost everyone measured 5 1/8 inches.  Finally, we asked everyone to program their robots to turn both wheels 5 rotations and measure again.  This time some kids got measurements of 25 inches, 25.5 inches and others 26 inches.  So now we know how far the robot moves per each wheel rotation.

Next week, we’ll put all of what we have learned so far into practice.  We will give the kids a “Rescue” mission, where the robots start from base and should be programmed to fetch a  stranded Lego figure/pet from a given location and bring it back to base.  It should be lots of fun.  Also, if you can, go over some of these concepts with your kids at home.  We went over them very quickly during the meeting, but this is where they get to apply the theoretical knowledge that they learn in school to real life situations.  Try asking them to figure out how far your car moves for each rotation of your car’s wheels.