Apparatus 17 wherein {HEAD ~ the included angle} of the tapering section is {TAIL ~ at least twice the angle} whose tangent equals the static coefficient of friction between the test contact member and the test probe 
is
Apparatus 17 wherein { HEAD ~ the included angle } of the tapering section is { TAIL ~ at least twice the angle } whose tangent equals the static coefficient of friction between the test contact member and the test probe
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH