The RPM of "D" is 600 and hobbed with 48...

Question 1 of 270705eccefa3bacbc34ba4d47cd9

The RPM of "D" is 600 and hobbed with 48 teeth. If gears "A", "B", and "C" have 84, 66, and 22 teeth respectively, the RPM of "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

• Gear ratio between two meshed gears is inversely proportional to their number of teeth (more teeth = slower speed). • Overall speed ratio in a compound gear train is the product of each individual gear pair’s ratio. • Direction of rotation may change with each mesh, but RPM magnitude depends on tooth counts and which gears are on the same shaft.

💭 Think About

• Start from gear D (you know its RPM and teeth) and work step-by-step back through gears C, B, and A using tooth ratios. • Identify which gears are rigidly connected on the same shaft so they share the same RPM, and which are only meshed and therefore have inverse speed ratios. • After you compute the theoretical RPM of A, compare it to the choices and think about whether a large driving gear should speed up or slow down the driven gear.

✅ Before You Answer

• Be sure you are pairing the correct meshing gears in each step (D with C, then B with A, etc., as shown in the illustration). • Confirm that for each mesh you apply: N₁ × RPM₁ = N₂ × RPM₂, where N is number of teeth. • Double-check that you have multiplied (not divided) the intermediate ratios in the correct sequence for a compound train before selecting your final RPM.