Passage 1: The Impact of Agricultural Runoff on Lake Ecosystems

Eutrophication is a process that occurs when a body of water becomes overly enriched with minerals and nutrients. This frequently happens due to agricultural runoff. When farmers apply nitrogen and phosphorus-based fertilizers to their crops, heavy rains can wash the excess chemicals into nearby lakes and rivers.

These excess nutrients act as a massive food source for phytoplankton and algae, causing an “algal bloom” – a rapid growth of algae on the water’s surface. While algae produce oxygen during the day, the thick layer blocks sunlight from reaching underwater plants, causing them to die. More critically, when the massive amount of algae eventually dies, bacteria begin to decompose the dead organic matter. This decomposition process consumes vast amounts of dissolved oxygen (DO) in the water. As oxygen levels plummet, fish suffocate and die, leading to a “dead zone.”

Passage 2: The Physics of Roller Coasters

At the very top of the highest hill (Point A), the roller coaster car possesses maximum Gravitational Potential Energy (PE), calculated by PE = mgh. As the car plummets down, its height decreases, meaning its PE decreases. However, its speed dramatically increases. This lost PE is transformed into Kinetic Energy (KE), calculated by KE = ½mv².

At the very bottom (Point B), PE is nearly zero, but KE is at its absolute maximum. Due to friction with the tracks, some mechanical energy is converted into thermal energy (heat), meaning the car will never reach its initial height of Point A again without an external motorized pull.

Passage 3: The Ring of Fire and Tsunamis

One of the most devastating consequences of tectonic activity in the Ring of Fire is the generation of tsunamis. When a convergent boundary ruptures underwater—specifically when a heavier oceanic plate subducts under a lighter continental plate—the sudden upward snap displaces a massive volume of water.

In the open ocean, a tsunami wave might be only a few feet high and travel at speeds exceeding 500 mph. As it approaches shallow waters, speed decreases due to friction. According to energy conservation, as the wave’s kinetic energy (speed) decreases, its potential energy (height) must increase, building a towering wall of water.

PASSAGE 1: Antibiotic Resistance (Kháng sinh)

When bacteria are exposed to antibiotics, most die. However, a few may possess a random genetic mutation making them naturally resistant. They survive, reproduce, and over time, the entire population becomes resistant due to natural selection.
Data Table (% bacteria killed): 2010 (98%) -> 2015 (85%) -> 2020 (50%) -> 2025 (15%).

PASSAGE 2: Crash Testing (Thử nghiệm va chạm)

Momentum (p = m × v). Force (F = Δp/t). Cars use “crumple zones” that crush easily during a crash. By crushing, these zones increase the time (t) it takes to stop.

PASSAGE 3: Greenhouse & Albedo (Hiệu ứng nhà kính)

Greenhouse Effect traps heat. “Albedo” is sunlight reflected back. White ice = high albedo. Dark ocean = low albedo (absorbs heat). Melting ice exposes dark ocean -> lower albedo -> absorbs more heat -> more ice melts (Positive feedback loop).