Explicit physics instruction
Impulse equals change in momentum and also area under a force-time graph. Different force-time shapes can deliver the same impulse.
A longer interaction time for the same Δp generally reduces average force, which is central to padding and safety-system design.
Peak force and average force are not identical; the graph shape matters.
Vocabulary: impulse; force-time graph; area; average force; peak force.
Worked example with reasoning
A triangular force pulse with base 0.20 s and peak 100 N has area ½(0.20)(100)=10 N·s, matching a 10 kg·m/s momentum change.
Guided question
Design two different force-time pulses with the same area and compare likely peak forces.
Independent work
- Calculate impulse from two rectangular/triangular graphs.
- Match each impulse to a momentum change.
- Explain how padding can change peak force without changing total impulse much.
Misconception check
Longer stopping time does not eliminate momentum change; it changes the force-time profile.
Formative understanding check
What graph quantity equals impulse?
Reveal response
Area under the force-time curve.
Mentor evidence conference
Ask Archaemenes to compare momentum, energy, and impulse representations for consistency.
Teacher guidance
Foundation: Use area counting and simple shapes.
Core: Connect graph area with Δp and average force.
Extended: Compare two pulses with equal area but different peaks and discuss design implications.