Explanation:
The engine, which is a reciprocating internal combustion engine, has to operate within a narrow speed range (typically between 1000 and 6000 RPM) in order to produce efficient combustion and minimize wear and tear. However, the wheels need to be able to rotate at much wider range of speeds, from a standstill to over 100 mph.
Using gears allows the engine to operate at its optimal speed while still providing the necessary torque at the wheels to propel the car. The transmission, which is a set of gears, allows the driver to select the appropriate gear ratio for the desired wheel speed.
For example, when starting from a standstill, the driver selects a low gear (low gear ratio) to provide high torque to the wheels. As the car accelerates, the driver can shift to higher gears (higher gear ratios) to maintain the engine speed within its optimal range while still increasing the wheel speed. The same principle applies when decelerating and climbing hills: selecting lower gears provides engine braking and increases the available torque.
In addition to providing different gear ratios, gears also allow for reverse motion by reversing the direction of rotation. This is accomplished through a separate gear in the transmission called the reverse gear.
Ultimately, gears are essential for cars because they enable them to operate efficiently, accelerate smoothly, and overcome resistance such as hills and loads, while keeping the engine within its optimal operating conditions.
