The velocity may be measured by the use of {TAIL ~ light screens}, which measure the time required for the ball to travel {HEAD ~ a fixed distance} 
The velocity may be measured by the use of { TAIL ~ light screens } , which measure the time required for the ball to travel { HEAD ~ a fixed distance }
OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD