Reaction Time

Reaction Time: Students time how long it takes to catch a dropped ruler

Materials

Ruler (older kids) or yardstick (younger kids)

Directions

  • Hold the ruler near the end and let it hang down
  • Have another person put his or her hand at the bottom of the ruler and have them ready to grab the ruler (however, they should not be touching the ruler)
  • Tell the other person that you will drop the ruler sometime within the next 5 seconds and that they are supposed to catch the ruler as fast as they can after it is dropped
  • Record the level (inches or centimeters) at which they catch the ruler
  • Test the same person 3 times (vary the time of dropping the ruler within the 5 second "drop-zone" so the other person cannot guess when you will drop the ruler)

    Alternative Experiments

    • Have the person catching close their eyes
      • Say "drop" when dropping the ruler
      • Or tap their foot when dropping the ruler
        How does reaction time change from having eyes open? Which method is faster/slower?
    • Try the experiment in dim light. Does reaction time increase, decrease, or stay the same? Can you explain your results?
    • Compare boys vs. girls. On average, are the boys or girls faster?
    • Compare different ages. Who is faster - the older students or younger students?
    • Compare the scores after practice. Does reaction time improve with practice?
    • Compare kids' scores vs. parents' scores. Who is faster?

    Discussion Points

    • In the first experiment, the signal needs to pass from the eyes, to the brain, to the spinal cord and then out to the muscles
    • In the alternative experiments, the signal either travels from the ear (saying drop) or from the foot (tapping the foot) before heading to the brain. 
    • There are times when reaction time isimportant, such as pain reflexes, like when you step on something sharp or touch something hot