Lesson 7: Friction, Air Resistance (Drag) & Terminal Velocity
Exploring forces, net force calculations, motion graphs, energy, and real-world NZ physics applications.
🎯 Ngā Whāinga Akoranga | Learning Intentions
Friction and drag as opposing motion forces, factors affecting friction (surface texture, contact area, lubrication) and drag (speed, surface area, streamline shape), and terminal velocity.
Investigate friction coefficients across surfaces, model skydiver falling motion, and explain why terminal velocity occurs when drag equals weight force (F_net = 0 N).
🎥 Media Anchor & Pedagogical Scaffold
Air Resistance & Terminal Velocity Physics
Video Clip: Friction and drag — how resistive forces work and what terminal velocity means (Runtime: 3m 14s).
🧠 1. Before Viewing (Activate & Predict)
Why does a falling skydiver stop accelerating and reach a constant maximum speed long before hitting the ground?
👁️ 2. During Viewing (Watch With a Job)
- Define: what is drag, and what factors does the video identify as affecting how large the drag force is?
- Explain: describe in steps why a skydiver reaches terminal velocity — what happens to acceleration as drag increases?
- Apply: why does a crumpled piece of paper fall faster than a flat sheet of the same mass? Use force language.
🗣️ 3. After Viewing & Kaiako Move (Process & Apply)
Kaiako Move: Drop coffee filters individually and nested together to demonstrate terminal velocity in the classroom.
Immediate Task: Complete Worksheet 7: Skydiver Terminal Velocity Force Arrow Sequence & Coffee Filter Lab Log.
⚡ Whakaoho | Do Now: Drop Them Together
A flat sheet of paper, and the same sheet screwed into a tight ball. Identical mass. Two minutes: predict which lands first and why — then actually drop them.
The mass did not change. Something else did, and naming that something is the whole lesson.
📖 Activity 1: Measure Friction, Then Model the Skydiver
Four surfaces (13 min). Drag the same block across four surfaces with a spring balance and record the force needed for each. Control what you can — same block, steady speed, same pulling angle — then rank the surfaces and say what physical difference produced the ranking.
Three moments of a fall (12 min). Sketch a skydiver just after jumping, while speeding up, and at terminal velocity. Draw both force arrows at each stage, to scale. Terminal velocity is the moment the two arrows are the same length — write down what Fnet equals at that instant, and what the skydiver is doing.
📝 Activity 2: Year 10 Physics Worksheet & Explanation Scaffolding (20 mins)
Logbook Section 7. Record: (1) your four-surface results with the variables you controlled listed; (2) three skydiver diagrams with arrows drawn to scale; (3) an explanation of terminal velocity using the words drag, weight and net force — and stating why the skydiver stops accelerating without stopping falling.
🏫 Kaiako Planning & Pedagogy Notes
Year 10 Curriculum Alignment: NZ Curriculum Phase 4 Science — Physical World strand. Builds foundational physics problem-solving skills for NCEA Level 1 Mechanics and Level 2 Physics.