What is the difference between a V-belt drive and a timing-belt drive in terms of power transmission?

• A. V-belts transmit power mainly by friction with grooves; timing belts transmit torque with teeth to prevent slip and maintain timing.
• B. V-belts transmit torque with teeth to prevent slip; timing belts rely on friction.
• C. Both transmit power solely by hydrodynamic lubrication.
• D. V-belts transmit power completely by teeth; timing belts rely on friction.

Answer: (A)

The key idea is how the belt drives the pulley. V-belts transfer power mainly through friction in the contact area between the belt and the pulley grooves. The belt presses into the grooves, and the friction at that interface does the turning; this means some slip can occur if the load is high or conditions change, so timing and precise synchronization aren’t guaranteed.

Timing belts, on the other hand, have teeth that mesh with matching teeth on the pulleys, creating a positive engagement. This teeth-and-pulley contact prevents slip, so rotation stays synchronized and timing is maintained. That difference—friction-based transmission versus tooth-driven positive engagement—is what sets them apart in how they transmit power.

The other statements aren’t correct because V-belts don’t rely on teeth, and timing belts don’t operate primarily by friction; hydrodynamic lubrication isn’t the governing mechanism for either in typical drive scenarios.