• Quick retrieval from earlier learning (Uniform acceleration: v² − u² = 2 a s). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. An object starts at 4 m/s and accelerates uniformly at 3 m/s² over 50 m. What is its final velocity, in m/s? (Give 1 decimal place.) → 17.8 m/sPrompt: Use v² − u² = 2 a s.
2. A car travelling at 15 m/s brakes with a deceleration of 10 m/s². What is its braking distance, in m? (Give 1 decimal place.) → 11.3 mPrompt: Final velocity v = 0.
3. A train speeds up from 10 m/s to 25 m/s over 100 m. What is its acceleration, in m/s²? (Give 2 decimal places.) → 2.63 m/s²Prompt: a = (v² − u²) ÷ (2 s)

• Drop a sheet of paper and a scrunched-up sheet together and ask why one falls faster.
• Share the objective: Horizontal projectiles: time of flight and range. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: A ball is kicked horizontally off a cliff 45 m high. Ignoring air resistance, how long does it take to reach the beach below, in s? (g = 9.8 m/s²; give 2 decimal places)
• Step 1: t = √(2 × 45 ÷ 9.8) = 3.03
• Step 2: So the answer is: 3.03 s
• Answer: 3.03 s
• Pause after each step and ask a student to say what comes next.

• Do these together. Students try each step on whiteboards before you reveal it.
• Use the hints as prompts rather than giving the answer.

1. A ball is kicked horizontally off a cliff 5 m high. Ignoring air resistance, how long does it take to reach the beach below, in s? (g = 9.8 m/s²; give 2 decimal places) → 1.01 sPrompt: Vertical motion starts from zero vertical velocity.
2. A stone is thrown horizontally at 10 m/s from a cliff 19.6 m high. How far from the base of the cliff does it land, in m? (g = 9.8 m/s²; ignore air resistance) → 20 mPrompt: Find the time of flight from the vertical motion.

• Students work on the student sheet. Circulate and check the first two answers of every student early.
• Students who finish: write a question of their own for a partner, with the answer.

The 8 questions are on the student sheet below, with answers in the key.

• Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

1. During a projectile's flight (no air resistance), what happens to its horizontal velocity? (it stays constant / it increases / it reverses / it decreases to zero) → it stays constantPrompt: Which force acts horizontally?
2. A ball is kicked horizontally off a cliff 20 m high. Ignoring air resistance, how long does it take to reach the beach below, in s? (g = 9.8 m/s²; give 2 decimal places) → 2.02 sPrompt: Vertical motion starts from zero vertical velocity.

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-12.