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Science lesson plan · 8th grade (Year 9 in England) · 60 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 · 6 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 ball of paper / they always land together / the flat sheet / neither falls) → the flat sheetPrompt: They have the same mass. What is different?
  2. Cyclists crouch low over their handlebars in races. Why? (to increase friction with the road / to make the bike heavier / to see the road better / to reduce air resistance) → to reduce air resistancePrompt: Air pushes against the front of a moving body.
  3. Why does a parachute slow a skydiver down? (It is full of helium / Its large surface creates a lot of air resistance / It makes the skydiver lighter / It turns off gravity) → Its large surface creates a lot of air resistancePrompt: The parachute pushes against lots of air.

Hook · 6 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 · 12 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 · 12 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. You push on a wall with 50 N. What force does the wall exert on you? (0 N / 50 N, pushing back on you / 100 N / 25 N) → 50 N, pushing back on youPrompt: Forces come in pairs.
  2. Newton's laws: which statement is true? (For every force there is an equal and opposite force on the other object. / 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.) → 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 · 17 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 · 7 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 true? (A bigger resultant force gives a bigger acceleration for the same mass. / Heavier objects need less force to accelerate. / The two forces in a Newton's third law pair act on the same object. / A moving object needs a constant force to keep moving at steady speed in space.) → A bigger resultant force gives a bigger acceleration for the same mass.Prompt: Think about inertia, F = ma and action–reaction pairs.
  2. Newton's laws: which statement is NOT true? (A resultant force makes an object accelerate. / An object at rest stays at rest unless a resultant force acts on it. / For every force there is an equal and opposite force on the other object. / The two forces in a Newton's third law pair act on the same object.) → 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?

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. Seat belts help stop passengers continuing forward in a crash.
    • B. The two forces in a Newton's third law pair act on the same object.
    • C. An object at rest stays at rest unless a resultant force acts on it.
    • D. For every force there is an equal and opposite force on the other object.
  2. Question 2

    Newton's laws: which statement is true?

    • A. The two forces in a Newton's third law pair act on the same object.
    • B. An object at rest stays at rest unless a resultant force acts on it.
    • C. Heavier objects need less force to accelerate.
    • D. A moving object needs a constant force to keep moving at steady speed in space.
  3. Question 3

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

    • A. Newton's third law
    • B. Ohm's law
    • C. Hooke's law
    • D. Newton's first law (inertia)
  4. Question 4

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

    • A. The rocket becomes lighter than air
    • B. The gas pushes the rocket upwards with an equal and opposite force
    • C. Gravity switches off
    • D. The air underneath lifts it like a balloon
  5. Question 5

    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
  6. Question 6

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

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

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Answer key: Newton's laws of motion

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

  2. 2. B. An object at rest stays at rest unless a resultant force acts on it.

  3. 3. D. Newton's first law (inertia)

  4. 4. B. The gas pushes the rocket upwards with an equal and opposite force

  5. 5. D. the empty trolley

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