If Z1 equals Z2 in a simple gear pair, what is the gear ratio and speed relation?

• A. Gear ratio is Z2/Z1; speed_out = speed_in × Z1/Z2; torque_out = τ_in × Z2/Z1 × η
• B. Gear ratio is Z1/Z2; speed_out = speed_in × Z2/Z1; torque_out = τ_in × Z1/Z2 × η
• C. Gear ratio is 1:1; speed_out = speed_in; torque_out = τ_in × η
• D. Gear ratio is Z2/Z1; speed_out = speed_in × Z2/Z1; torque_out = τ_in × Z1/Z2 × η

Answer: (C)