Final answer:
In a planetary gear system with the sun gear stationary, the arm as the input, and the ring gear as the output to achieve a velocity ratio of 4:3, the number of teeth on the ring gear must be calculated relative to the sun gear and the arm to achieve the desired velocity ratio.
Step-by-step explanation:
To solving this problem related to a planetary gear train with a specified overall velocity ratio of 4:3, we need to apply our understanding of the mechanics involved in gear systems. Given that the sun gear is stationary, the arm is the input, and the ring gear is the output, we need to determine the relationship between the number of teeth on the sun gear and the ring gear to achieve the target ratio. Typically, the number of teeth on the ring gear (output) compared to the sun gear (fixed) would determine the velocity ratio when the arm is the input.
This scenario doesn't directly correspond to the static relationships between gear teeth since one gear is fixed, and we require a velocity ratio between the arm (carrier) and the ring gear. However, we can infer that the ring gear must have more teeth than the sun gear to facilitate the required velocity ratio. Without a direct formula to calculate the direct relationship between the number of teeth on the gears given the stated conditions, we cannot conclusively state which of the provided options (A to D) is correct.