Also provided is a variable weight loading device on the sample holder for loading the sample holder such that a selected load can be applied to {HEAD ~ the sample} normal to {TAIL ~ the friction surface}, and a force measurement device for obtaining a measurement indicative of the frictional force resisting such relative movement between the sample holder and the friction surface effected by the motion device 
normal to
Also provided is a variable weight loading device on the sample holder for loading the sample holder such that a selected load can be applied to { HEAD ~ the sample } normal to { TAIL ~ the friction surface } , and a force measurement device for obtaining a measurement indicative of the frictional force resisting such relative movement between the sample holder and the friction surface effected by the motion device
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