Correct

Incorrect

shafts are arranged parallel and rotate in the opposite directions

shafts are arranged parallel and rotate in the same directions

shafts are arranged at right angles and rotate in one definite direction

driven shaft is to be started or stopped whenever desired without interferring with the driving shaft

Acme threads

Square threads

Buttress threads

Multiple threads

pulley is made the weakest

key is made the weakest

key is made the stongest

all the three are designed for equal strength

4 mm

5 mm

6 mm

7 mm