While the slide is in motion, {TAIL ~ rolling friction characteristics} are measured by {HEAD ~ a force gauge} 
While the slide is in motion , { TAIL ~ rolling friction characteristics } are measured by { HEAD ~ a force gauge }
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD