Crash Test Car Experiment: 7 Easy Steps to Learn Collision Physics and Car Safety

Crash Test Car

Roll toy cars into barriers with different padding materials and discover why car safety engineering is entirely about controlling how long a collision takes.

Overview of crash test car

The Crash Test Car experiment brings automotive safety physics into the classroom with nothing more than toy cars, a ramp, and a collection of padding materials. A toy car rolls down a ramp and collides with a barrier. By changing what the barrier is padded with — hard foam, soft cotton, bubble wrap, or nothing at all — students can observe, measure, and reason about why some collisions do more damage than others.

The core concept is impulse: the same change in momentum can be delivered over a very short time with enormous force, or over a longer time with gentle force. A car stopping in ten milliseconds against a concrete wall generates very different forces than the same car stopping in one hundred milliseconds against a crumple zone. Real car safety engineering — airbags, crumple zones, seatbelts — is entirely built around this principle. Students who run this experiment leave with a physical intuition for why every millisecond of collision duration matters.

Time: 25–35 minutes   Complexity: Beginner to Intermediate   Setup: Toy car, ramp, barrier materials, optional force measurement

Activity Materials Required

The required materials for Crash Test Car activity are:

•       A toy car (a heavier die-cast car works better than a light plastic one)
•       A smooth ramp approximately 60–80 cm long (a plank of wood, a ruler, or a folded cardboard ramp)
•       A solid barrier block — a stack of books or a wooden block
•       Padding materials: bubble wrap, cotton wool, foam, cardboard, newspaper, nothing (for baseline)
•       A ruler for measuring ramp height
•       A raw egg or a small clay figure placed on the car (optional, to visually represent a passenger)
•       A stopwatch (optional)
•       A phone with slow-motion video (optional, for measuring collision duration)

Step-by-Step Instructions

The steps to be followed for crash test car:

1.     Set up the ramp at a fixed angle — use a book under one end and mark the height. Keep this consistent across all trials.
2.     Place the car at the top of the ramp with no padding on the barrier. Release the car and observe the collision. If using an egg or clay figure, note what happens to it.
3.     Attach bubble wrap to the front of the barrier. Repeat the ramp release from the same height. Compare the collision to the baseline.
4.     Replace bubble wrap with cotton wool, then foam, then crumpled newspaper. Run one trial per material, always from the same ramp height.
5.     Rank the materials from hardest to softest collision and record your observations.
6.     Optional: Use slow-motion video to count frames during the collision. Estimate collision duration for hard versus padded barriers.
7.     Discuss: which material produced the longest collision duration? Which produced the gentlest impact on the passenger figure?
   

   

Science Behind the Crash Test Car Activity

• Momentum is mass multiplied by velocity. When a car stops, its momentum changes from a finite value to zero — this change in momentum is called impulse.
• The impulse-momentum theorem states that impulse equals force multiplied by time. For a given change in momentum, a shorter collision time requires a greater force, and a longer collision time requires a smaller force.
• A hard barrier stops the car almost instantly — enormous force, very short time. A padded barrier extends the collision duration, reducing the peak force proportionally.
• This is why airbags inflate in milliseconds and deflate slowly: they maximize the time over which the driver decelerates, minimizing the force on the body. Crumple zones in real cars are engineered to collapse progressively, achieving the same effect at a much larger scale.

Pro Tip: For the best Crash Test Car Experiment results, place a small clay figure on the roof of the car before each trial. The figure’s behavior in each collision — staying put, sliding forward, or flying off — gives an immediate visual representation of the forces experienced by a passenger. Children respond strongly to this and it anchors the discussion in human consequence.

Expected Results of Crash Test Car Experiment

With no padding, the car stops abruptly and the passenger figure is flung forward. With bubble wrap or foam, the collision takes noticeably longer and the figure moves less violently. Cotton wool typically gives the longest collision duration and the gentlest passenger response. Students consistently rank the results correctly when asked to order materials from most to least dangerous.

What Did You Learn from the Crash Test Car Experiment?

After completing the Crash Test Car Experiment, you learned how increasing collision time reduces impact force and helps protect passengers. The Crash Test Car Experiment also showed how engineers use physics to design safer vehicles with airbags, seatbelts, and crumple zones.

• Impulse reduces impact force. A longer stopping time lowers the force during a collision.
• Soft padding improves safety. Bubble wrap and foam absorb impact by increasing collision time.
• Momentum affects crashes. Heavier or faster cars create stronger impacts.
• Car safety features use physics. Airbags and crumple zones reduce injuries by extending stopping time.
• Engineering relies on testing. Comparing different materials helps design safer vehicles.

Conclusion

The Crash Test Car experiment makes impulse tangible. The same momentum change — same car, same speed, same stop — produces wildly different forces depending on how long the collision takes. This is the founding principle of vehicle safety design, and it is fully demonstrable with a toy car and a roll of bubble wrap. Physics saves lives, and this experiment shows exactly how.

Frequently Asked Questions

1. What is impulse and how is it different from force?

Impulse is the product of force and the time over which that force acts. A large force over a short time and a small force over a long time can produce the same impulse — and therefore the same change in momentum. The padding changes the time, not the total impulse.

2. Why do cars have crumple zones if they make the car more damaged?

Crumple zones are designed to absorb energy and extend collision time by deforming progressively. The car is replaceable; the passenger is not. A zone that crumples over a longer time dramatically reduces the peak force on the occupants, even though the car looks worse afterward.

3. Why does the clay figure fly forward when the car stops suddenly?

The figure has momentum in the direction of travel. When the car stops suddenly, the figure continues moving forward — Newton’s first law. Without a seatbelt or airbag to apply a gradual backwards force, it flies free. This is exactly what happens to unbelted passengers in real crashes.

4. Does the mass of the car affect the results of crash car test activity?

Yes. A heavier car has more momentum at the same speed and therefore delivers a greater impulse at the barrier. In real crash testing, vehicle mass is carefully controlled to make comparisons valid.

5. What happens if you increase the ramp height?

A higher ramp gives the car more speed at the bottom — and since momentum is mass times velocity, more momentum. The collision forces increase, and the padding needs to extend the collision time even further to produce the same gentle stop.

6. How do airbags relate to this Crash Test Car experiment?

Airbags inflate in approximately 30 milliseconds and then begin deflating as the passenger presses against them. This engineered sequence extends the deceleration time of the passenger’s head and torso from a few milliseconds (hard surface) to 50–100 milliseconds — dramatically reducing peak force on the skull and brain.