Whacko-meter

The whacko-meter is an easy to assemble device that can measure initial momentum and energy of an object that strikes (whacks) it.  This work has been sent for publication to the American Journal of Physics - Apparatus Notes (not accepted as of yet).

 

You may get a pre-print pdf of the paper here.

 

A macro embedded in a blank Excel spreadsheet is available below.  The macro enables rapid calculation of the stop time, peak voltage of the signal, and the average signal size. 

Instructions for the macro

    1)    download the blank spreadsheet.  click here.

    2)    start Excel

    3)    go to tools options security macro security...   

            Then select medium security (otherwise the macro will be inaccessible).

    4)    The macro assumes data values in 5 columns (columns A through E) and 2500 rows (rows 1 through 2500).  Ideally, the data  in these columns represent 5 trials under identical conditions using a Tektronic oscilloscope (this is why its defaulted to 2500 values).  In practice, I found that 25 msec/division was an ideal scale and it is defaulted into the macro.  In order to find a reasonable zero level, the trigger must be set up so that the oscilloscope trigger is beyond the third division.  The macro is operated by the following: go to tools Macro Macro...

Then select run Analyze_whacko.

The program will then determine the stop time, peak voltage, and average signal size with standard deviations.