Grade 8 · Systems in Action · Systems, Work, and Efficiency
Trace Energy Through a Bicycle System
A system combines interacting components to perform a function. Describing its inputs, processes, outputs, boundaries, feedback, losses, and users reveals how safely and efficiently it operates.
Visual model
See how the ideas connect
For students
Notice, predict, explain
Choose one part of the model. Predict how it connects to another part, then use the lesson evidence to explain your thinking.
For teachers
Pause for science talk
Show the model before the explanation. Ask “What do you notice?” and “What might change?” Then revisit student ideas after the worked example.
The big idea
System performance depends on relationships between components
Mechanical advantage changes the relationship between input and output force and displacement, while friction, deformation, vibration, and sound dissipate energy and reduce efficiency.
Work it through
Analyse a bicycle climbing a hill
- Step 1 The rider supplies force through the pedals over a circular displacement, doing work on the drivetrain.
- Step 2 Crank, chain, gears, wheels, frame, brakes, and controls interact to transfer forces and motion safely.
- Step 3 Selecting a lower gear changes mechanical advantage so less pedal force is needed, but more pedal movement is required for a given wheel rotation.
- Step 4 Lubrication, alignment, tire pressure, maintenance, clear instructions, and effective brakes reduce losses and improve safe operation.