Resonant Tuning Fork Pair on Pine Boxes with Mass and Mallet, 440Hz cylinder Copper-block plug key switch with

Copper-block plug key switch with two 4mm terminals and a removable plastic-guarded plug

Brass-wire conductor and seven plotting compasses on a clear base

Acrylic bell-in-vacuum jar with an internal 4-6V DC electric bell that fades and falls silent as the enclosed air is removed

Flexible spine model demonstrates vertebral movement

Low-noise 220V blower with a detachable 60-inch hose and adjustable flow control

Resonant Tuning Fork Pair on Pine Boxes with Mass and Mallet, 440Hz cylinder Copper-block plug key switch withUsed to demonstrate beat frequencies and sympathetic resonance, this pair of 440Hz steel forks sits on pine resonance boxes (7. 5 x 4 x 2. 5 inches) with one fork carrying an adjustable tuning mass.