Answer Key: EV3 - Move until Near_Unit_Level

Answer Key: Unit Quiz

  1. The Ultrasonic sensor emits high frequency sound (higher than the human ear can detect) and measures the time it takes for this sound to echo/reflect back to the sensor.  By dividing this roundtrip time in half and knowing what the speed of sound is, the sensor can provide a reading of the distance to an object (in centimeters or inches).
  2. A threshold is a cut-off value that divides a range of numbers into two groups – those above the threshold and those below.
  3. The Ultrasonic sensor uses less-than (<) to define “near” and greater-than (>) to define “far”.
  4. The robot will likely not appear to move.  The first Move-unlimited block will turn the motors on and immediately run the next block.  The second Wait-for-Ultrasonic block will detect the object is indeed greater-than 12 inches away and immediately run the next block.  The third block will stop the motors and if this Move block is set to “Brake” the robot will not appear to Move (if set to coast it would roll forward for a short distance).