Gear mechanisms are systems that use interlocking gears to transmit motion and force. Gears are circular objects with teeth that mesh together, allowing them to transfer rotational energy from one gear to another. This mechanism is commonly found in machines, vehicles, and clocks, where precise movement is essential. The arrangement of gears can change the speed and torque of the output motion. For example, when a small gear drives a larger gear, the larger gear turns more slowly but with greater force. This principle is crucial in applications like bicycles, where gear ratios help optimize performance for different terrains.