As the pulley ratio increases in a belt drive system, what happens to shaft speed and torque on the driven pulley?

As the pulley ratio increases in a belt drive system, what happens to shaft speed and torque on the driven pulley?

• A. Increase; increase
• B. Decrease; remain the same
• C. Increase; decrease
• D. Decrease; increase

Answer: (D)

In a belt drive system, the pulley ratio significantly impacts the relationship between shaft speed and torque. When the pulley ratio increases, it means that the diameter or size of the driving pulley in relation to the driven pulley is larger. As a result of this increased ratio, the driven pulley rotates slower than the driving pulley. This leads to a decrease in shaft speed for the driven pulley, aligning with the mechanics of belt drive systems where the input and output speeds are inversely related to the sizes of the pulleys. Simultaneously, the torque is affected. When the speed of the driven pulley decreases due to the increased pulley ratio, the torque, which is a measure of rotational force, increases. This is because torque is inversely proportional to speed in a given power system. The power transmitted remains constant (in ideal conditions), so as the speed decreases, torque must increase to maintain that constant output power. Therefore, within the context of this question, as the pulley ratio increases, the shaft speed of the driven pulley decreases while the torque increases.

In a belt drive system, the pulley ratio significantly impacts the relationship between shaft speed and torque. When the pulley ratio increases, it means that the diameter or size of the driving pulley in relation to the driven pulley is larger.

As a result of this increased ratio, the driven pulley rotates slower than the driving pulley. This leads to a decrease in shaft speed for the driven pulley, aligning with the mechanics of belt drive systems where the input and output speeds are inversely related to the sizes of the pulleys.

Simultaneously, the torque is affected. When the speed of the driven pulley decreases due to the increased pulley ratio, the torque, which is a measure of rotational force, increases. This is because torque is inversely proportional to speed in a given power system. The power transmitted remains constant (in ideal conditions), so as the speed decreases, torque must increase to maintain that constant output power.

Therefore, within the context of this question, as the pulley ratio increases, the shaft speed of the driven pulley decreases while the torque increases.