Quadratic Beads


Beads on a string separated by quadratic distances hit the ground at equal time intervals.

The quadratic beads string
The quadratic beads string



Principles Illustrated

Constant acceleration due to gravity causes the distance fallen by an object to increase proportional to the square of time.

Asking students to make the quadratic beads string using ordinary nuts is a very good exercise in numeracy and scaling.

Download sound file (right-click and “save link as”, 36 KB sound only): Quadratic_Bead_Sound.mp4

NCEA & Science Curriculum

SCI 1.1, PHYS 2.4


Attach beads or nuts or some other dense objects to a string with quadratic spacing starting with perhaps 5 cm and working up to close to 1 metre. When dropped, the beads hit the floor with a constant separation in time. When a second string with uniformly spaced beads is dropped the beads hit with decreasing separation in time.

Larger Photo


Individual teachers are responsible for safety in their own classes. Even familiar demonstrations should be practised and safety-checked by individual teachers before they are used in a classroom.

Related Resources

Film a dropping ball and use VideoPoint to analyse the motion.

Teaching Resources

Would you like to contribute lesson suggestions? Contact us.


PIRA 1C20.20


This teaching resource was developed with support from

The MacDiarmid Institute
Faculty of Science, Victoria University of Wellington
School of Chemical and Physical Sciences, Victoria University of Wellington


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