AST Earth and Physical Science 1 — Questions and Answers
Question 1: Which layer of Earth is composed primarily of liquid iron and nickel?
- Crust
- Mantle
- Outer core (Correct answer)
- Inner core
Correct answer: Outer core
The outer core is made of liquid iron and nickel and generates Earth's magnetic field.
Earth's structure from outside in: crust (solid rock), mantle (semi-solid silicate rock), outer core (liquid iron and nickel), and inner core (solid iron and nickel under extreme pressure). The outer core's moving liquid iron creates Earth's magnetic field through the dynamo effect.
Question 2: The process by which water vapor in the atmosphere cools and becomes liquid water is called:
- Evaporation
- Transpiration
- Condensation (Correct answer)
- Precipitation
Correct answer: Condensation
Condensation occurs when water vapor loses energy and changes state to liquid water.
Condensation is the phase change from gas (water vapor) to liquid water when air cools to its dew point. It is responsible for cloud formation, fog, and dew. The water cycle includes evaporation (liquid → gas), condensation (gas → liquid), and precipitation (liquid falling to Earth).
Question 3: According to Newton's second law of motion, force equals:
- mass × velocity
- mass × acceleration (Correct answer)
- weight × speed
- momentum × time
Correct answer: mass × acceleration
Newton's second law: F = ma (Force = mass × acceleration).
Newton's second law states F = ma. Force (measured in newtons) equals the product of mass (kg) and acceleration (m/s²). It explains why a heavier object requires more force to accelerate at the same rate as a lighter object. This law underlies classical mechanics.
Question 4: Which type of rock forms when magma cools and solidifies?
- Sedimentary
- Metamorphic
- Igneous (Correct answer)
- Composite
Correct answer: Igneous
Igneous rocks form from the cooling and solidification of magma or lava.
The three rock types: Igneous (formed from cooled magma/lava — e.g., granite, basalt), Sedimentary (formed from compressed sediment — e.g., sandstone, limestone), Metamorphic (formed from existing rocks altered by heat/pressure — e.g., marble, slate). Igneous rocks are the original source material in the rock cycle.
Question 5: The Richter scale measures the:
- Depth of an earthquake
- Magnitude of seismic energy released (Correct answer)
- Speed of tectonic movement
- Duration of ground shaking
Correct answer: Magnitude of seismic energy released
The Richter scale quantifies the magnitude (energy) of an earthquake.
The Richter scale, developed by Charles Richter in 1935, measures earthquake magnitude on a logarithmic scale — each whole number increase represents 10× more ground motion and ~31.6× more energy release. The Moment Magnitude Scale (Mw) has largely replaced it for large earthquakes but uses similar principles.
Question 6: What causes the seasons on Earth?
- Changes in Earth's distance from the Sun
- The tilt of Earth's axis as it orbits the Sun (Correct answer)
- Differences in the Moon's gravitational pull
- Variations in solar flare activity
Correct answer: The tilt of Earth's axis as it orbits the Sun
Earth's axial tilt causes different hemispheres to receive varying amounts of sunlight throughout the year.
Earth's 23.5-degree axial tilt means that as it orbits the Sun, each hemisphere alternately tilts toward or away from the Sun. When tilted toward the Sun, that hemisphere receives more direct sunlight → summer. When tilted away → winter. Earth is actually closest to the Sun in January (Northern Hemisphere winter), disproving the distance theory.
AST Earth and Physical Science 1
Which layer of Earth is composed primarily of liquid iron and nickel?