Question

part 9 - mechanical comprehension question 7 of 15 when the gear train shown is operating, which set of gears turn in the same direction? a f and i b g and j c g, i, and j d f, h, and j click the button or type the letter next to your answer.

Explanation:

Step1: Recall Gear Direction Rule

Meshed gears (directly touching) turn in opposite directions. Gears with an odd number of intermediate gears (or same - level non - meshed through odd intermediates) turn in the same direction.

Step2: Analyze Each Gear Pair

• Gear F and G: Meshed, so opposite directions.
• Gear G and H: Meshed, so opposite directions (so H is same as F).
• Gear H and I: Meshed, so opposite directions (so I is opposite to H, same as G).
• Gear I and J: Meshed, so opposite directions (so J is opposite to I, same as H and F).

Now let's check each option:

• Option A: F and I. F and G (opposite), G and H (opposite, so H same as F), H and I (opposite, so I opposite to F). So F and I are opposite. Eliminate A.
• Option B: G and J. G and H (opposite), H and I (opposite, so I same as G), I and J (opposite, so J opposite to I, same as G). So G and J are same. Wait, let's re - check. Wait, F - G (opposite), G - H (opposite, H same as F), H - I (opposite, I same as G), I - J (opposite, J same as H (and F)). Wait, maybe a better way: Count the number of meshes between gears. For two gears, if the number of meshes between them is even, they turn same; if odd, opposite.
• For F and I: Number of meshes between F - G (1), G - H (2), H - I (3). Odd number of meshes, so opposite.
• For G and J: G - H (1), H - I (2), I - J (3). Odd? Wait no, G to H (1), H to I (2), I to J (3). Wait, no, the path from G to J: G - H (mesh 1), H - I (mesh 2), I - J (mesh 3). Wait, no, the number of meshes between G and J is 3? Wait, no, G is meshed with H (1), H with I (2), I with J (3). So the number of gear - to - gear meshes between G and J is 3 (odd), so they should be opposite? Wait, maybe my initial approach was wrong. Let's use the "idler gear" concept. An idler gear (like H) changes the direction between two gears. So:
• F and G: opposite (G = -F)
• G and H: opposite (H=-G = F)
• H and I: opposite (I=-H=-F)
• I and J: opposite (J=-I = F)
• Now, G=-F, J = F. Wait, that can't be. Wait, no, let's list the direction of each gear:
• Let's assume F turns clockwise. Then G turns counter - clockwise (opposite). H turns clockwise (opposite to G, same as F). I turns counter - clockwise (opposite to H, same as G). J turns clockwise (opposite to I, same as H and F).
• So F: clockwise, G: counter - clockwise, H: clockwise, I: counter - clockwise, J: clockwise.
• Now check option D: F, H, J. F (clockwise), H (clockwise), J (clockwise). They turn in the same direction.
• Option B: G (counter - clockwise) and J (clockwise) - opposite. Eliminate B.
• Option C: G (counter - clockwise), I (counter - clockwise), J (clockwise). G and I same, but J different. Eliminate C.
• Option D: F (clockwise), H (clockwise), J (clockwise). Same direction.

Answer:

D. F, H, and J