(MCQ) Why do buildings fall in earthquakes? - Vicki V. May

1. What is one of the biggest risks during an earthquake?

• A. Water shortages

• B. Collapsing buildings

• C. Fire hazards

• D. Ground splitting apart

Answer explanation

Key from transcript:
"Collapsing buildings posing one of the largest risks." (0:13 - 0:17)

Explanation: The transcript states that collapsing buildings are a major danger in earthquakes, not ground splitting or water issues.

2. Why do most buildings NOT collapse due to the ground splitting apart?

• A. The ground never moves during an earthquake

• B. Most buildings are not on a fault line

• C. Earthquakes happen only underground

• D. Buildings are too heavy to fall

Answer explanation

Key from transcript:
"For one thing, most buildings are not located right on a fault line." (0:35 - 0:39)

Explanation: The transcript explains that buildings are not usually located directly on fault lines, so ground splitting isn't the main reason they collapse.

3. What do architects and engineers use to understand how buildings react to earthquakes?

• A. Special cameras

• B. Computer games

• C. Mathematical models

• D. Earthquake-proof floors

Answer explanation

Key from transcript:
"Architects and engineers use models." (0:46 - 0:55)

Explanation: Engineers use models to study building reactions, not cameras or games.

4. What happens when the ground moves during an earthquake?

• A. The entire building moves at the same time

• B. The top of the building shakes more than the bottom

• C. Only the roof moves

• D. The building stays still

Answer explanation

Key from transcript:
"When the ground moves beneath a building, it displaces the foundation and lower levels, sending shock waves through the rest of the structure." (1:20 - 1:26)

Explanation: The movement starts from the foundation and moves upward, making the top shake more.

5. How does height affect a building’s reaction to earthquakes?

• A. Taller buildings are always safer

• B. Shorter buildings are always safer

• C. Shorter buildings shift less, taller ones are more flexible

• D. Short buildings always collapse first

Answer explanation

Key from transcript:
"Shorter buildings tend to be stiffer and shift less, while taller buildings are more flexible." (1:51 - 1:54)

Explanation: The transcript states that shorter buildings move less, but taller buildings are flexible, which affects their stability.

6. Why did midsized buildings collapse more than others in the 1985 Mexico City earthquake?

• A. They were not built properly

• B. Their frequency matched the earthquake’s frequency

• C. They were too old

• D. They were made of weak materials

Answer explanation

Key from transcript:
"The frequency of the earthquake's seismic waves happened to match the natural frequency of the midsized buildings." (3:17 - 3:20)

Explanation: The concept of resonance caused these buildings to shake more than others.

7. What is the natural frequency of a building?

• A. The rate at which it naturally vibrates

• B. The number of floors in a building

• C. The speed at which people leave the building

• D. The amount of electricity used

Answer explanation

Key from transcript:
"A building's natural frequency, determined by its mass and stiffness, is the frequency that its vibrations will tend to cluster around." (2:51 - 2:55)

Explanation: Natural frequency is how often a building vibrates naturally.

8. How do engineers prevent buildings from collapsing due to resonance?

• A. They remove all windows

• B. They change the building’s natural frequency

• C. They add more floors

• D. They stop earthquakes from happening

Answer explanation

Key from transcript:
"Engineers work with geologists and seismologists to predict the frequency of earthquake motions at building sites in order to prevent resonance-induced collapses." (3:44 - 3:48)

Explanation: Engineers design buildings to avoid matching earthquake frequencies.

9. What is base isolation?

• A. A system that isolates the building’s foundation from shaking

• B. A way to move the building to a safer location

• C. A special alarm system

• D. A stronger roof

Answer explanation

Key from transcript:
"Base isolation uses flexible layers to isolate the foundation’s displacement from the rest of the building." (4:14 - 4:21)

Explanation: Base isolation allows the foundation to move separately from the building, reducing shaking.

10. What is the main idea of the transcript?

• A. How to survive an earthquake

• B. How engineers design earthquake-resistant buildings

• C. Why earthquakes happen

• D. The history of earthquakes

Answer explanation

Key from transcript:
"In the end, it's not the sturdiest buildings that will remain standing but the smartest ones." (4:29 - 4:33)

Explanation: The transcript focuses on engineering solutions for earthquake-resistant buildings.