The RPM of gear "D" is 900 and it is hobbed...

Question 1 of 270705eccefa3bacbc34ba4d47cd4

The RPM of gear "D" is 900 and it is hobbed with 48 teeth. If gears "A", "B", and "C" have 88, 66, and 22 teeth respectively, the RPM of gear "A" in the gear train illustration is ________. See illustration MO-0088.

Back

Question 1 of 27070

No Illustration

This question does not have an illustration

🔍 Key Concepts

• Relationship for meshed gears: speed (RPM) is inversely proportional to number of teeth so that $N_1 T_1 = N_2 T_2$ . • In a compound gear (two gears rigid on the same shaft, like gears B and C in the illustration), both gears spin at the same RPM. • Overall train ratio from gear D to gear A is the product of the tooth ratios of each meshing pair. Start at known RPM (gear D) and work step‑by‑step to gear A.

💭 Think About

• From the illustration, which gears are clearly on the same shaft, and what does that tell you about their RPMs? • Write the equation for the speed ratio between D and C, then between B and A. How can you combine these to relate the RPM of D directly to the RPM of A? • After you compute the theoretical RPM of A, compare it with 900 RPM. Should gear A be turning faster or slower than gear D, based on their relative effective sizes through the train?

✅ Before You Answer

• Be sure you treat each meshed pair separately: D with C, then B with A. • Confirm that you used inverse proportion: when a gear with more teeth drives one with fewer teeth, the smaller gear turns faster, and vice versa. • After calculating the RPM of A, check that your result is consistent with the direction of reduction or increase you expect from the overall train before selecting from the answer choices.