Technology Systems and Applied Problem Solving
This domain tests applied problem solving in technological systems: describing a system by its inputs, processes and outputs, applying the design process against a set of specifications, and calculating quantities such as gear ratios, mechanical advantage or scale on a technical drawing.
Systems thinking
- Inputs - energy, material and information entering the system.
- Process - the transformation, which is the function.
- Outputs - the intended product plus by-products such as heat, noise or waste.
- Feedback - a signal from the output that adjusts the process; a thermostat is the standard example.
- Systems contain subsystems: a bicycle includes a transmission subsystem and a braking subsystem.
The design process
Specifications define the problem through function, constraints and criteria. Constraints are non-negotiable limits (budget, maximum mass, safety standard, supply voltage); criteria are optimised (durability, cost, ease of use). The cycle runs: define, research, sketch or prototype, test, evaluate against the specifications, improve. A technical drawing is a communication, so it needs a scale, a title block, dimensions in millimetres and a legend.
Mechanisms
- Gear train: ratio = teeth on driven gear ÷ teeth on driver gear. The driven gear turns more slowly by that factor, with proportionally greater torque.
- Pulley systems: a movable pulley halves the effort force but doubles the rope length pulled.
- The trade-off is universal: force and speed cannot both be gained.
- Efficiency = useful output energy ÷ input energy, and is always below 100 % because of friction and heat.
Worked example
A 12-tooth driver gear on a motor spins at 120 rpm and meshes with a 36-tooth driven gear. Ratio = 36 ÷ 12 = 3. Output speed = 120 ÷ 3 = 40 rpm. The output torque is roughly three times the motor torque minus friction losses, so the system trades speed for force. That is well matched to lifting a heavy load slowly.
Traps
- Inverting the gear ratio by multiplying when you should divide.
- Forgetting that real machines lose energy, so output work is less than input work.
- Confusing a constraint with a criterion, or proposing a solution that violates a stated constraint.
- Reading a technical drawing without checking its scale and units.
- Describing what a device is instead of what it does; always state the function first.