Why does an automatic transmission car not move when reversing without pressing the accelerator?

[TheoLynn]

Automatic transmission cars do not move when reversing without pressing the accelerator because the power between the engine and transmission is transmitted through a torque converter. When reversing or moving forward, if the car is driven at idle speed, the engine power is insufficient to overcome the ground friction resistance, so the car will not move backward or forward. Automatic transmission generally refers to the car's automatic gear-shifting mechanism. While driving, the control system of the automatic transmission automatically selects the appropriate gear based on the engine speed and load, replacing the driver's subjective judgment of timing and gear-shifting operations. Typically, automatic transmission cars have six gear positions, from top to bottom: P, R, N, D, S, and L.