Pendulum waves

Safe­ty pre­cau­tions

None.

Equip­ment

• 1m rod;
• clamps;
• thread;
• or­na­ments.

Step-by-step in­struc­tions

A pen­du­lum wave is a phys­i­cal ef­fect based on a se­ries of in­de­pen­dent pen­du­lums that are fine­ly tuned rel­a­tive to their os­cil­la­tion pe­ri­ods (or fre­quen­cies). We se­cured 15 in­de­pen­dent­ly-swing­ing pen­du­lums to a sta­ble frame. Each pen­du­lum has a dif­fer­ent sus­pen­sion length, and thus a dif­fer­ent os­cil­la­tion fre­quen­cy. The long­est pen­du­lum makes 51 os­cil­la­tions per minute, and each fol­low­ing short­er pen­du­lum com­pletes one more os­cil­la­tion per minute than the pre­vi­ous. This caus­es the pen­du­lums to "dance" in waves.

Process de­scrip­tion

The os­cil­la­tion pe­ri­od of a sim­ple pen­du­lum de­pends not on its mass, but rather on its sus­pen­sion length. When we tilt the pen­du­lum out of its po­si­tion of equi­lib­ri­um, it ac­quires po­ten­tial en­er­gy. When re­leased, it be­gins to move as grav­i­ty acts on it, com­plet­ing an arc di­rect­ly pro­por­tion­al in length to its sus­pen­sion length. The os­cil­la­tion pe­ri­od is the time it takes the pen­du­lum to re­turn to its ini­tial po­si­tion. A longer pen­du­lum cov­ers a greater dis­tance and moves slight­ly more quick­ly, but its os­cil­la­tion pe­ri­od is longer none­the­less. Short pen­du­lums thus os­cil­late at a greater fre­quen­cy than long pen­du­lums. By ad­just­ing the lengths of the pen­du­lums, you can cre­ate beau­ti­ful mov­ing pat­terns.