Beads on a string separated by quadratic distances hit the ground at equal time intervals.
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.
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.
Film a dropping ball and use VideoPoint to analyse the motion.
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