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Science lesson plan · 8th grade (Year 9 in England) · 45 minutes

Newton's laws of motion

Forces and motion

CCSS NGSS.MS-PS2-1CCSS NGSS.MS-PS2-2CCSS NGSS.HS-PS2-1England: KS3 Physics: Motion and forcesEngland: KS4 Combined Science: Forces and motion

Objective and success criteria

Students will: Newton's laws of motion.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Balanced and unbalanced forces; Air resistance and water resistance

Leads to: Force, mass and acceleration (F = ma)

Materials: Force meters, Toy cars and ramps, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 5 min

  • Quick retrieval from earlier learning (Balanced and unbalanced forces; Air resistance and water resistance). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Why does a parachute slow a skydiver down? (It is full of helium / It makes the skydiver lighter / It turns off gravity / Its large surface creates a lot of air resistance) → Its large surface creates a lot of air resistancePrompt: The parachute pushes against lots of air.
  2. Which falls slowest: a flat sheet of paper or the same paper screwed into a ball? (the flat sheet / neither falls / the ball of paper / they always land together) → the flat sheetPrompt: They have the same mass. What is different?
  3. Why are fish and boats streamlined (smooth and pointed)? (to float higher / to reduce water resistance / to increase water resistance / to look nice) → to reduce water resistancePrompt: A streamlined shape lets water flow past easily.

Hook · 5 min

  • Drop a sheet of paper and a scrunched-up sheet together and ask why one falls faster.
  • Share the objective: Newton's laws of motion. Read the success criteria together.

I do: model it · 10 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: A passenger lurches forward when a bus brakes suddenly. Which law explains this?
  • Step 1: An object keeps moving at the same velocity unless a resultant force acts (inertia).
  • Step 2: So the answer is: Newton's first law (inertia)
  • Answer: Newton's first law (inertia)
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 10 min

  • 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 rocket pushes exhaust gas downwards. Why does the rocket go up? (Gravity switches off / The rocket becomes lighter than air / The air underneath lifts it like a balloon / The gas pushes the rocket upwards with an equal and opposite force) → The gas pushes the rocket upwards with an equal and opposite forcePrompt: Rockets also work in space, where there is no air.
  2. Newton's laws: which statement is true? (An object at rest stays at rest unless a resultant force acts on it. / The two forces in a Newton's third law pair act on the same object. / Heavier objects need less force to accelerate. / A moving object needs a constant force to keep moving at steady speed in space.) → An object at rest stays at rest unless a resultant force acts on it.Prompt: Think about inertia, F = ma and action–reaction pairs.

You do: independent practice · 10 min

  • 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 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 5 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Newton's laws: which statement is NOT true? (Seat belts help stop passengers continuing forward in a crash. / An object at rest stays at rest unless a resultant force acts on it. / The two forces in a Newton's third law pair act on the same object. / A resultant force makes an object accelerate.) → The two forces in a Newton's third law pair act on the same object.Prompt: Which two objects does each force in a pair act on?
  2. A rocket pushes exhaust gas downwards. Why does the rocket go up? (The air underneath lifts it like a balloon / The gas pushes the rocket upwards with an equal and opposite force / Gravity switches off / The rocket becomes lighter than air) → The gas pushes the rocket upwards with an equal and opposite forcePrompt: Rockets also work in space, where there is no air.

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Balanced and unbalanced forces.
  • Use concrete materials: force meters.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Move on to: Force, mass and acceleration (F = ma).
  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-8.

Free lesson plan from eurekami.com/lesson-plan-builder

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Newton's laws of motion

Name

Date

Score/ 6

  1. Question 1

    Newton's laws: which statement is NOT true?

    • A. For every force there is an equal and opposite force on the other object.
    • B. An object at rest stays at rest unless a resultant force acts on it.
    • C. The two forces in a Newton's third law pair act on the same object.
    • D. A resultant force makes an object accelerate.
  2. Question 2

    A rocket pushes exhaust gas downwards. Why does the rocket go up?

    • A. The rocket becomes lighter than air
    • B. Gravity switches off
    • C. The gas pushes the rocket upwards with an equal and opposite force
    • D. The air underneath lifts it like a balloon
  3. Question 3

    Newton's laws: which statement is true?

    • A. Heavier objects need less force to accelerate.
    • B. A moving object needs a constant force to keep moving at steady speed in space.
    • C. The two forces in a Newton's third law pair act on the same object.
    • D. A bigger resultant force gives a bigger acceleration for the same mass.
  4. Question 4

    The same force is applied to an empty trolley and a full one. Which accelerates more?

    • A. both the same
    • B. the full trolley
    • C. neither moves
    • D. the empty trolley
  5. Question 5

    A passenger lurches forward when a bus brakes suddenly. Which law explains this?

    • A. Newton's third law
    • B. Hooke's law
    • C. Newton's first law (inertia)
    • D. Ohm's law
  6. Question 6

    You push on a wall with 50 N. What force does the wall exert on you?

    • A. 100 N
    • B. 25 N
    • C. 50 N, pushing back on you
    • D. 0 N

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Answer key: Newton's laws of motion

  1. 1. C. The two forces in a Newton's third law pair act on the same object.

  2. 2. C. The gas pushes the rocket upwards with an equal and opposite force

  3. 3. D. A bigger resultant force gives a bigger acceleration for the same mass.

  4. 4. D. the empty trolley

  5. 5. C. Newton's first law (inertia)

  6. 6. C. 50 N, pushing back on you