IBC Quiz #185
26/12/2025
Lakshmi N
Class 8
G R International Public school
Hema G S
Class 8
Sri Vasavi Vidya samsthe sira
Sathvik
Class 8
Vidya Shanti school
Note: Quiz prizes will be awarded to ten randomly selected students who submit correct answers before the deadline. Winners will be declared on the website and the weekly newsletter.
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Previous Week Quizzes
IBC Quiz #185
December 26, 2025
A curious child named Shelvin designs his own version of chess by expanding the board to 10 × 10, adding two extra pawns and two special power pieces per side: the Witch and the Sacrificing Warrior.
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Witch: Moves like a King. Once per game, if a friendly piece is immediately to its left or right, it may copy that piece’s movement for one move only.
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Sacrificing Warrior: Moves like a Knight. When placed on a new square, it may sacrifice itself to eliminate all adjacent enemy pieces, after which the Warrior is also removed from the board.
Piece values: Pawn 1, Bishop 3, Knight 3, Rook 5, Witch 6, Sacrificing Warrior 7, Queen 9.
Assume that the Witch has not yet used its special ability.
It is Black’s move. Black must prioritise the following:
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Checkmate,
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Escaping check orcheckmate,
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Capturing the maximum possible points.
Based on the given board position, which option is the correct move for Black?
A curious child named Shelvin designs his own version of chess by expanding the board to 10 × 10, adding two extra pawns and two special power pieces per side: the Witch and the Sacrificing Warrior.
-
Witch: Moves like a King. Once per game, if a friendly piece is immediately to its left or right, it may copy that piece’s movement for one move only.
-
Sacrificing Warrior: Moves like a Knight. On its third move, all adjacent enemy pieces are eliminated, and the Warrior is also removed from the board.
Piece values: Pawn 1, Bishop 3, Knight 3, Rook 5, Witch 6, Sacrificing Warrior 7, Queen 9.
Assume that the Sacrificing Warrior has completed its two moves and Witch has not yet used its special ability.
It is Black’s move. Black must prioritise:
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Checkmate,
-
Escaping check/checkmate,
-
Capturing the maximum points.
Based on the given board position, which option is the correct move for Black?
IBC Quiz #184
December 19, 2025
A warehouse operates a manual cargo hoist to lift 200 kg loads from the ground floor to the first floor. Workers turn a hand wheel to apply effort, and this motion is transferred through a single-stage gear pair to a lift drum. The lift drum winds a rope to raise the load.
Workers have reported excessive physical strain during operation. Management has observed that very slow lifting reduces productivity. As a result, the gear system must be redesigned to balance human effort, mechanical efficiency, and lifting time.
Current System
|
Parameter |
Value |
|
Load weight (WLoad) |
200 kg |
|
Lift height (h) |
4 m |
|
Lift drum |
60 teeth |
|
Drive wheel |
30 teeth |
|
Gear ratio (ROld) |
2.0:1 (60 teeth / 30 teeth) |
|
Worker force (FOld) |
100 kg |
|
Time per lift (TOld) |
40 s |
|
Mechanical efficiency (ηOld) represents the ratio of useful output work to input work in the current system |
90% |
Design Constraints
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Fatigue constraint: The worker’s force must not exceed 65 kg
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Time constraint: The lifting time must not exceed 70 seconds
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Mechanical limits: The Lift drum must have no more than 90 teeth and the Drive wheel must have at least 18 teeth
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Efficiency constraint: For every increase of 1.0 in gear ratio above 2.0, the mechanical efficiency decreases by 5% due to frictional losses.
ηNew = 90% − 5% × (R − 2)
Hints
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Effort Change: Worker force decreases as the gear ratio increases. A higher gear ratio reduces force, but it also reduces mechanical efficiency and increases the required effort. Both effects must be considered together.
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Time Change: Lifting time is directly proportional to the gear ratio, as higher ratios require more hand-wheel rotations.
Question
Which single-stage gear pair configuration satisfies all the constraints simultaneously?
A warehouse uses a manual cargo hoist operated by workers turning a large handwheel to lift loads of 200 kg from the ground floor to the first floor. The hoist is primarily used to move boxes of goods between storage levels during peak operating periods. Motion from the handwheel is transmitted through a single-stage gear pair to a lift drum, which winds a rope to raise the load.
Workers have reported significant fatigue due to the required effort, and management seeks to redesign the gear system to reduce effort without increasing lifting time excessively or reducing efficiency.
Current System
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Drive wheel: 30 teeth
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Lift drum: 60 teeth
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Gear ratio (Lift drum teeth/ Drive wheel teeth): 2.0:1
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Worker force at the wheel rim: 100 kg.
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Rotations per lift: 8
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Time per lift: 40 seconds
(Assume mechanical losses are negligible.)
Engineering Goal
Modify the gear system to reduce the physical effort required by the worker while maintaining acceptable operational efficiency.
Design Constraints
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Fatigue constraint: Worker force must not exceed 60 kg.
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Efficiency constraint: Time per lift must not exceed 70 seconds.
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Lift drum limit: Maximum of 90 teeth.
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Drive wheel limit: Minimum of 18 teeth.
Question
Which single gear modification satisfies both the fatigue and efficiency constraints?
