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

broken belt

broken belt and its adjacent belts

all the belts

there is no need of changing any one as remaining belts can take care of transmission of load

inertia

momentum

moment of momentum

torque