Science lesson plan · 11th grade (Year 12 in England) · 45 minutes
Force and rate of change of momentum (safety design)
Forces and motion
CCSS NGSS.HS-PS2-3CCSS NGSS.HS-ETS1-2England: GCSE Combined Science: Forces (Physics only: changes in momentum)
Objective and success criteria
Students will: Force and rate of change of momentum (safety design).
- 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: Momentum (p = m v)
Leads to: the next skill in this area.
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 (Momentum (p = m v)). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- What is the momentum of a 1200 kg object moving at 3 m/s, in kg m/s? → 3600 kgm/sPrompt: momentum = mass × velocity
- An object of mass 2 kg has a momentum of 50 kg m/s. What is its velocity, in m/s? → 25 m/sPrompt: Rearrange p = m v.
- Two identical trolleys move towards each other at the same speed. What is their total momentum? (it cannot be worked out / half one trolley's momentum / zero / double one trolley's momentum) → zeroPrompt: Opposite directions have opposite signs.
Hook · 5 min
- Drop a sheet of paper and a scrunched-up sheet together and ask why one falls faster.
- Share the objective: Force and rate of change of momentum (safety design). 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 80 kg passenger moving at 15 m/s is brought to rest in 0.4 s by a seat belt and airbag. What is the average force on the passenger, in N?
- Step 1: Δp = 80 × 15 = 1200 kg m/s
- Step 2: F = 1200 ÷ 0.4 = 3000
- Step 3: So the answer is: 3000 N
- Answer: 3000 N
- 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.
- A 70 kg passenger moving at 10 m/s is brought to rest in 0.5 s by a seat belt and airbag. What is the average force on the passenger, in N? → 1400 NPrompt: F = change in momentum ÷ time
- A helmet increases the time for a head to stop in a fall from 0.05 s to 0.2 s. The change in momentum is the same. By what factor is the average force reduced? → 4Prompt: F = Δp ÷ t, so force is inversely proportional to time.
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 8 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.
- A 60 kg passenger moving at 15 m/s is brought to rest in 0.5 s by a seat belt and airbag. What is the average force on the passenger, in N? → 1800 NPrompt: F = change in momentum ÷ time
- How do crumple zones in a car reduce injuries? (They reduce the change in momentum to zero / They make the car heavier / They increase the time taken to stop, so the force on passengers is smaller / They stop the car instantly) → They increase the time taken to stop, so the force on passengers is smallerPrompt: F = Δp ÷ t
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: Momentum (p = m v).
- 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
- 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-11.
Free lesson plan from eurekami.com/lesson-plan-builder