decrease the variation of speed

to control

to control SN

all of the above

Hartung governor

Wilson Hartnell governor

Pickering governor

Inertia governor

ball bearing

roller bearing

needle roller bearing

thrust bearing

in increasing velocity ratio

in decreasing the slip of the belt

for automatic adjustment of belt position so that belt runs centrally

increase belt and pulley life

for changing the direction of motion of the belt

for applying tension

for increasing -velocity ratio

all of the above