demonstrations:newtons_cradle
Newton's Cradle
Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★☆☆ Minimal safety procedures required
Categories: Energy, Force, Motion
Alternative titles:
Summary
A Newton’s cradle demonstrates conservation of momentum and energy through swinging metal spheres that collide in sequence. When one or more spheres are released, the same number of spheres on the opposite side swing out with nearly identical motion.
Procedure
- Pull back one of the spheres in the cradle to a small angle and release it.
- Observe that one sphere on the opposite side swings out with the same motion.
- Repeat the experiment with two, three, or four spheres pulled back and released together.
- Note how the same number of spheres exit on the opposite side, while the middle spheres remain nearly stationary.
Links
Newton's Cradle - Incredible Science:
Giant Newton's Cradle - Mythbusters - Banijay Science:
📄 Newton's Cradle - Classroom Physics Demos: https://demos.smu.ca/demos/mechanics/136-newton-s-pendulum
Variations
- Try releasing spheres from a larger angle to see how the motion changes.
- Release one sphere from each end at the same time and watch the interactions in the middle.
- Use different sized Newton’s cradles to compare motion with larger or smaller spheres.
Safety Precautions
- Ensure the Newton’s cradle is placed on a stable surface to prevent it from tipping over.
- Keep fingers clear of the moving spheres to avoid pinching.
Questions to Consider
- Why does the same number of spheres swing out on the opposite side as were released? (Because momentum and energy are transferred through the line of spheres.)
- Why do the middle spheres appear to stay still? (They transfer energy and momentum but do not visibly move.)
- What energy transformations occur during the collisions? (Kinetic energy transfers between spheres, with small amounts lost as sound and heat.)