Tech Support: Gravity Drop



Helpful Tips

  • The biggest challenge when using this piece of equipment is aligning the dropper and catcher. If these are not aligned properly, the ball will not fall cleanly through the photogates. If the ball does not pass correctly through the photogates, the beam will not be broken by the diameter of the ball, and the resulting speed calculations will be invalid. To align the dropper and catcher properly, use the plumb line and bob provided with the kit. Directions for use are provided. You will level the base of the physics stand by adjusting the three leveling feet.
  • Each time you release the marble, listen to the sound it makes when it falls into the catcher. A "good drop" is one where the marble falls directly into the catcher without hitting the sides of the hole. You will hear a "thunk" from a good drop, and you will hear a slight clicking sound if it is a bad drop and it hits the side of the hole. Discard trials that give the clicking sound.
  • Be sure to place the dropper and catcher the correct distance apart, as indicated in the investigation instructions. This distance has been chosen to increase your chances of collecting valid data.
  • Make sure to use the plumb line to assist you in aligning the marble dropper with the catcher.
  • The catcher is always attached to the bottom hole of the physics stand.
  • The dropper is always placed at the 11th hole on the physics stand.
  • There is a ball of modeling clay in the bottom of the catcher. This clay absorbs the energy of the falling marble which keeps it from bouncing out. After many drops the clay flattens out and must be reformed into a pillow for the marble to land on. Roll clay in your fingers to soften it.


Q: The data I'm recording for each trial varies widely. How can I prevent this from happening?

A: This experiment requires careful technique. Preparing the stand so that it is level, and properly aligning the catcher and dropper takes time and patience. This experiment is not recommended for students that have poor motor skills, or below average frustration tolerance.