Final answer:
The most common application for planetary gear-sets is in automotive transmissions.
Step-by-step explanation:
The most common application for planetary gear-sets is in automotive transmissions. Planetary gear-sets are used to achieve different gear ratios and torque conversions in a compact and efficient manner. They offer advantages such as high power transmission, smooth operation, and the ability to handle large amounts of torque.
In an automotive transmission, a planetary gear-set consists of a sun gear at the center, planet gears that revolve around the sun gear, and a ring gear that encloses the planet gears. By engaging different combinations of these gears, it is possible to achieve different gear ratios and torque output.