Tackling Physics: Momentum, Collisions and Concussions Explained Through Football Plays

Hook: Why students and teachers struggle with collision physics — and how football solves it

Finding classroom-friendly, curriculum-aligned ways to teach momentum, impulse and collisions is hard. Textbook problems feel abstract and paywalled research can be inaccessible. For students and teachers who love sport, football plays provide vivid, real-world examples to make the maths and the human safety implications tangible. This article gives you classroom-ready demonstrations, clear calculations, and a balanced discussion of concussions and safety that reflect the latest trends through 2025–2026.

The core ideas up front (inverted pyramid)

Most important takeaways:

• Momentum (p = mv) governs how much motion a player carries into a collision and how difficult they are to stop.
• Impulse (J = Δp = FΔt) shows why increasing the contact time reduces peak force and can lower injury risk.
• Center of mass and torque explain why the location and angle of a tackle determine rotational accelerations that contribute to concussion risk.
• Collisions in football are largely inelastic: kinetic energy is not conserved; energy is transferred to deformation, heat, and body motion.
• Practical demos using toy carts, drop tests and video analysis can show these concepts safely in class. Safety-first guidance and concussion context based on 2024–2026 research trends are included.

1. Momentum on the pitch: Why a 240-lb linebacker feels unstoppable

Momentum is mass times velocity. A heavier or faster player carries more momentum into a play, making them harder to stop.

Worked example (use in class)

Choose realistic values teachers can relate to. Example: a linebacker of mass 110 kg (≈243 lb) running at 6 m/s (~13.4 mph) colliding with a running back of mass 95 kg (≈210 lb) running at 7 m/s (~15.7 mph) in the opposite direction:

• Linebacker momentum: p_L = 110 kg × 6 m/s = 660 kg·m/s
• Running back momentum: p_R = 95 kg × (−7 m/s) = −665 kg·m/s (direction convention)
• Total system momentum before collision ≈ −5 kg·m/s → near zero, so center of mass of the pair has little net motion; they will exchange energy and likely move together or fall.

Note how similar magnitudes but opposite signs lead to large internal forces and energy transfer during the tackle.

2. Impulse: Why the same momentum change can be more or less dangerous

Impulse links the change of momentum to the average force applied over the time of contact: J = Δp = FΔt. For a given Δp, increasing the contact time Δt reduces average force F.

Practical numbers teachers can use

Using the linebacker example: if the linebacker (p = 660 kg·m/s) is stopped to zero momentum by an opposing force:

• If stopping time Δt = 0.05 s (very abrupt), average force F ≈ 660 / 0.05 = 13,200 N
• If stopping time Δt = 0.25 s (softer, shoulder wrap, sliding), F ≈ 660 / 0.25 = 2,640 N

The same change in momentum produces far lower peak forces when the contact is stretched out — a core principle behind padding, tackling technique and helmet design.

3. Collisions: elastic, inelastic and what really happens in a tackle

In ideal physics, an elastic collision conserves kinetic energy; an inelastic collision does not. Football tackles are mostly inelastic: bodies deform, muscles absorb energy, and players often stick or tumble together.

Energy goes into:

• Deforming soft tissue and equipment
• Heat and sound
• Rotational and translational kinetic energy of the combined system

Understanding where energy goes helps explain why some hits cause concussions even when the total kinetic energy isn't enormous — it's the rapid transfer to the skull/brain and the resulting accelerations that matter.

4. Center of mass, torque and rotational accelerations — the concussion connection

Center of mass (CoM) determines how whole-body motion responds to external forces. When a tackle force does not pass through the CoM, a torque is generated and the body experiences rotation. For the head and brain, rotational accelerations are particularly harmful.

Consider two tackles of identical linear momentum:

• A wrap tackle around the waist increases Δt and applies force near the torso CoM — lower rotational acceleration.
• A high shoulder-to-head hit applies force above the head, far from the head/neck CoM — larger torque and higher angular acceleration of the head relative to the neck, raising concussion risk.

Recent biomechanics research through 2024–2025 emphasized rotational acceleration as a key predictor of concussion risk. By 2026, helmet testing and regulatory updates increasingly consider rotational metrics alongside linear accelerations.

5. Classroom and home experiments (safe, curriculum-ready)

Below are step-by-step demonstrations that model momentum, impulse and collisions using low-cost materials. All are designed for safety and for use in classrooms or physics clubs.

Experiment A — Conservation of momentum with low-friction carts

Objective: Show momentum conservation in 1D collisions and compute pre- and post-collision momenta.

Materials:

• Two low-friction dynamics carts (or toy air-track carts / skateboards on smooth floor).
• Spring bumper or Velcro pads.
• Meter stick, stopwatches or a smartphone slow-motion camera.

Procedure:

1. Measure cart masses m1 and m2.
2. Push cart 1 at speed v1 toward cart 2 (initially at rest) and film.
3. Use video to measure pre- and post-collision speeds, calculate p = mv for each cart.
4. Compare total momentum before and after; discuss sources of measurement error.

Analysis prompts:

• Is momentum conserved within measurement error? Why might observed kinetic energy drop?
• Relate the experiment to a football tackle — where does energy go during an inelastic tackle?

Experiment B — Impulse and padding: drop tests with accelerometer

Objective: Demonstrate that increased stopping time reduces peak acceleration (force) using a drop test.

Materials:

• Small dense ball (metal or dense rubber) or weighted mass.
• Smartphone with accelerometer app (many free apps exist) or a simple data-logger sensor.
• Hard surface and several layers of foam or a gel pad to simulate padding.

Procedure:

1. Affix the phone or sensor securely to the mass (safety first: use a camera mount or tape in teacher-controlled lab, not students holding it).
2. Drop from fixed height onto hard surface; record peak deceleration.
3. Repeat onto foam/gel that increases stopping time; record peak deceleration again.
4. Compare peak accelerations — relate drop height to incoming momentum, and padding to Δt.

Safety note: Do not use heavy or dangerous masses. Keep the experiment teacher-led and use safety goggles if fragments are possible.

Experiment C — Center of mass and torque with a human model

Objective: Show how force location relative to CoM affects rotation.

Materials:

• Long board or broomstick to represent a player's body, with marked CoM (midpoint) and additional small weights to change mass distribution.
• Soft foam pad to press or tap at different positions.

Procedure:

1. Balance the stick at the CoM to demonstrate neutral rotation when force passes through CoM.
2. Apply a short, horizontal impulse at the end of the stick and observe rotation about the CoM.
3. Discuss how a high hit on the head produces more rotational acceleration of the head than a low hit near the waist.

6. Linking experiments to real plays and safety strategies

Translate findings into actionable safety guidance used in coaching and equipment design:

• Teaching proper tackling technique (head up, wrap and drive) increases Δt and moves forces closer to the opponent's CoM — lowering peak forces and rotational torques.
• Effective padding and helmets aim to lengthen impact duration and spread forces across larger areas, though no helmet can completely prevent rotational accelerations.
• Rule changes that reduce high head contact and limit certain types of blocking create fewer high-torque events per game — a trend rule-makers pursued through 2024–2026.

7. Concussions: the biomechanics and classroom discussion points

Concussion is a clinical diagnosis related to brain dysfunction following head impact. From a physics standpoint, key contributors include:

• Linear acceleration — rapid straight-line changes in velocity.
• Rotational acceleration — angular velocity and acceleration that shear brain tissue.
• Impact location and neck stiffness — which moderate head motion.

In classroom conversations, emphasize that physics explains mechanisms and risk factors but not medical diagnosis; for safety and health care, defer to medical professionals and evidence-based protocols.

Trends in 2024–2026 and what teachers should know

Recent trends up to early 2026 relevant to teaching and safety:

• Helmet testing standards increasingly include rotational metrics alongside linear ones; manufacturers are innovating with materials and multi-layered liner systems.
• Wearable sensors (instrumented mouthguards, helmet accelerometers) and machine-learning algorithms are being adopted in elite programs to flag high-risk impacts in real time; many colleges and professional teams now use such systems for monitoring (use the data cautiously: sensors have limits and false positives).
• Coaching education emphasizes technique that lowers peak force and torque (e.g., shoulder-led tackles, neck-strength conditioning) as a non-gear intervention to reduce concussion risk.

All classroom materials and demos should stress that physics is only part of concussion prevention; clinical assessment, baseline testing and conservative return-to-play protocols are essential.

8. Lesson plan: 90-minute class session

Use this structure to teach the concepts with hands-on learning, aligned to secondary physics curricula.

1. 10 min — Hook & learning goals: present a short video clip of a tackle and pose physics questions.
2. 15 min — Mini-lecture: momentum, impulse, CoM, energy (equations and intuitive examples).
3. 40 min — Rotating lab stations: carts (momentum), drop test (impulse), CoM stick (torque).
4. 15 min — Data analysis & calculations: compute p, Δp, F estimates and compare across groups.
5. 10 min — Safety & concussion discussion: present trends, equipment limits and protocols.

9. Assessment ideas and exam-style questions

• Give masses and velocities of two players in a tackle and ask students to compute momentum and predict post-collision motion assuming an inelastic collision.
• Ask students to calculate average force if momentum change occurs over specified Δt, and explain the effect of doubling Δt on peak force.
• Short answer: describe why a hit to the head produces more rotational acceleration than a hit to the torso and the implications for concussion risk.

10. Safety and ethical considerations for any activity

Always prioritise participant safety. Recommended safeguards:

• Run physical demos with non-contact equipment (toy carts, sticks, sensors) — do not stage real tackles in class.
• When using phones as sensors, secure them in mounts and supervise drops to avoid injury or device damage.
• Emphasize that classroom physics does not replace medical judgement. If students raise concussion experiences, advise consulting qualified health professionals and school medical staff.

11. Bringing in 2026 tools: data analysis and AI

By 2026, accessible tools let students explore real-world sports data:

• Open-source video analysis tools (e.g., Tracker) let students extract velocities and accelerations from game footage for quantitative study.
• Public datasets and anonymised sensor logs from 2024–2026 projects allow classroom discussion of statistics, false positives and ethical data use.
• Introduce basic machine-learning classification tasks: given labeled impact events, students can explore features (peak acceleration, duration, rotational signal) that correlate with clinician-verified concussions — a good cross-disciplinary extension with computing classes.

12. Teacher resources and references (select reading)

Curate resources for deeper study:

• Physics and biomechanics review articles summarising momentum, impulse and head impact mechanics (search university libraries for up-to-date reviews through 2025).
• Manufacturer and standards bodies’ reports on helmet testing — look for NOCSAE and international test updates in 2024–2026.
• Open datasets and classroom guides for video analysis (Tracker documentary resources and university lab manuals).

Teachers: pair physics demonstrations with health education. Understanding the mechanics improves students’ critical thinking and helps them make informed choices about sport safety.

Final practical takeaways (ready-to-use)

• Use momentum examples with realistic masses and speeds — they stick in students’ minds.
• Run at least one impulse-based demo (drop test) to highlight how padding and technique reduce force.
• Discuss center-of-mass and torque with a simple stick model to show how head hits produce rotation.
• Embed concussion safety: teach limits of equipment, importance of technique, and the need to follow medical protocols.
• Leverage 2024–2026 trends: include machine-learning or sensor data units as enrichment for older students.

Call to action

Ready to bring collision physics to your classroom? Download our free lesson pack with student worksheets, step-by-step experiment guides, and a starter dataset for video analysis at naturalscience.uk/resources. Try the activities, share what works, and help build safer, evidence-based sport education for students and coaches in 2026.

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