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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. Which falls slowest: a flat sheet of paper or the same paper screwed into a ball? (the flat sheet / they always land together / the ball of paper / neither falls) → the flat sheetPrompt: They have the same mass. What is different?
  2. Cyclists crouch low over their handlebars in races. Why? (to reduce air resistance / to see the road better / to make the bike heavier / to increase friction with the road) → to reduce air resistancePrompt: Air pushes against the front of a moving body.
  3. Why are fish and boats streamlined (smooth and pointed)? (to reduce water resistance / to look nice / to float higher / to increase water resistance) → 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. The same force is applied to an empty trolley and a full one. Which accelerates more? (the full trolley / both the same / neither moves / the empty trolley) → the empty trolleyPrompt: a = F ÷ m
  2. Newton's laws: which statement is true? (The two forces in a Newton's third law pair act on the same object. / For every force there is an equal and opposite force on the other object. / Heavier objects need less force to accelerate. / A moving object needs a constant force to keep moving at steady speed in space.) → For every force there is an equal and opposite force on the other object.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. A passenger lurches forward when a bus brakes suddenly. Which law explains this? (Ohm's law / Newton's third law / Newton's first law (inertia) / Hooke's law) → Newton's first law (inertia)Prompt: The passenger keeps moving unless a force acts on them.
  2. Newton's laws: which statement is true? (Heavier objects need less force to accelerate. / A moving object needs a constant force to keep moving at steady speed in space. / The two forces in a Newton's third law pair act on the same object. / An object at rest stays at rest unless a resultant force acts on it.) → An object at rest stays at rest unless a resultant force acts on it.Prompt: Think about inertia, F = ma and action–reaction pairs.

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 true?

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

  2. Question 2

    Newton's laws: which statement is NOT true?

    • A. The two forces in a Newton's third law pair act on the same object.
    • B. Seat belts help stop passengers continuing forward in a crash.
    • C. An object at rest stays at rest unless a resultant force acts on it.
    • D. A resultant force makes an object accelerate.

  3. Question 3

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

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

  4. Question 4

    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

  5. Question 5

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

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

  6. Question 6

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

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

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Answer key: Newton's laws of motion

  1. 1. C. A bigger resultant force gives a bigger acceleration for the same mass.

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

  3. 3. A. the empty trolley

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

  5. 5. D. The gas pushes the rocket upwards with an equal and opposite force

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