Energy on the Riser: From Stillness to Motion

Festival context —Performers jumping from risers, lifting heavy props, and executing sustained dance sequences during the Cry of Jelicuon reenactment

S9FE-IIIa-21Grade 9 · Quarter 3Differentiate Potential and Kinetic Energy

Two Faces of Mechanical Energy in the Festival

Cry of Jelicuon troupe at dusk holding raised lanterns, still and at rest — Held up and still, each lantern stores **gravitational potential energy** in proportion to its height. Let one fall and that stored energy converts into the **kinetic energy** of motion.

In the Cry of Jelicuon, some of the most dramatic moments involve performers perched high on bamboo risers before executing a jump. At that frozen instant — standing motionless at height — they are a perfect example of gravitational potential energy. The moment they leap, that energy begins its transformation.

Gravitational Potential Energy (PE) is stored energy due to an object's position above a reference point: PE = mgh, where m is mass, g is 9.8 m/s², and h is height. The higher an object sits, the more energy it stores — energy that is ready to be released the moment the object moves.

Worked Example: Gravitational PE

A 55 kg performer stands motionless at the top of a 1.5 m bamboo riser, waiting for the cue to leap. How much gravitational potential energy is stored in their raised body? (use g = 9.8 m/s²)

Given

m=55 kgg=9.8 m/s²h=1.5 m

1FormulaPE = m × g × h

2SubstitutePE = 55 × 9.8 × 1.5

3AnswerPE = 808.5 J

All 808.5 J of this stored energy converts into kinetic energy as the performer falls and lands.

Comprehension Check

As a performer falls from the top of a riser to the ground, their potential energy as it transforms into kinetic energy.

Cry of Jelicuon performers raising tall props upright during the performance — **Cry of Jelicuon stage footage (New Lucena)** — performers raise the tall props upright. Raising mass to a height stores **gravitational potential energy** — `PE = mgh`; the higher they lift, the more PE is banked, ready to pour back out as motion (KE) when the props sweep down.

Kinetic Energy (KE) is the energy of motion: KE = ½mv². The moment the performer lands, they have converted all their PE into KE (ignoring air resistance). The heavier the performer and the taller the riser, the greater the kinetic energy at landing — and the louder the impact the audience hears.

From Sprint to Roll: Recycling Kinetic Energy

Cry of Jelicuon performers bursting from a held pose into full-speed synchronized motion — **Opening Salvo footage (New Lucena)** — the formation explodes out of a held pose into full-speed movement. Stored potential energy and muscular effort convert into **kinetic energy (`KE = ½mv²`)**: the faster the performers move, the more KE they carry — energy the choreography then recycles into rolls instead of wasting it on an abrupt stop.

Male performers in the war scene do not simply stop after a run — they transition fluidly into rolls across the stage floor. This is kinetic energy recycling in action: the kinetic energy built up during the sprint is carried into the roll, allowing the performer to dissipate the force of impact gradually while keeping the visual motion smooth. Rather than applying a large stopping force that abruptly cancels all KE, the rolling motion spreads the deceleration over a longer time and distance, protecting the body while sustaining the dramatic visual effect. The choreographer designs these transitions precisely because they are physically safer and visually more powerful than abrupt stops.

Worked Example: Kinetic Energy at Landing

The same 55 kg performer leaps from the 1.5 m riser. Falling freely, they reach a landing speed of about 5.4 m/s. How much kinetic energy do they carry at the instant they land?

Given

m=55 kgv=5.4 m/s

1FormulaKE = ½ × m × v²

2SubstituteKE = 0.5 × 55 × (5.4)² = 0.5 × 55 × 29.16

3AnswerKE ≈ 801 J

Landing speed from a 1.5 m drop is v = √(2gh) ≈ 5.4 m/s. The resulting KE (≈801 J) closely matches the initial PE (808.5 J) — the small difference is due to rounding.

Comprehension Check

The formula for kinetic energy is KE = ½mv², where v represents the object's .

Module Overview

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Riser Jump: Potential & Kinetic Energy Transformer