Required Equipment:
- Computer with Vernier LoggerPro software installed
- Vernier LabPro sensor interface
- Vernier force plate
- Helmet (can be picked up at local used sporting goods store for under $10)
- Heavy round mass, about 5kg - 10 kg
Setup:
The assembly of the demonstration is straightforward. Connect the output cable of the force plate to either CH1 or CH2 of the LabPro, and use the USB cable to connect the LabPro to a computer. Plug in the power cord of the LabPro and you're ready to go!
Depending on the mass of the object used, it may be necessary to protect the surface of the force plate. For my demonstration I added a file folder with a few papers in it on top of the force plate to prevent damage to the force plate.
It is also important to be able to measure the height the object is dropped from. I solved this problem by cutting two thin strips of paper exactly 10 cm long and attaching one to the bottom of the helmet and one to the bottom of the mass. When I dropped each object, I made sure that the piece of paper was hanging down and barely touching the surface of the force plate to ensure the mass would fall a height of 10 cm.
An example of this is shown in the video below:
Once everything is set up, play around with collecting data using LoggerPro! There are many tools that can be used in the program to analyze the data, the most important being the integral calculator. This will allow us to calculate the area under the Force vs. Time graphs produced, and therefore find the impulse of the collision.
Tips:
- Set the sampling rate of LoggerPro to its highest possible value (500Hz). This will ensure that as many data points as possible will be collected during the collision.
- Choose a mass that is rigid. A mass that is not rigid (such as a softer medicine ball filled with sand) could do a better job at cushioning the collision than a helmet! To properly model the human head the mass should not compress during the collision.