Science MCQs

Question 1

#1

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24 Jan 2026

The square of a planet’s orbital period is proportional to which power of the semi-major axis of its orbit?

Answer

Kepler's Third Law of Planetary Motion states that the square of a planet's orbital period (T) is directly proportional to the cube (power of 3) of the semi-major axis (a) of its orbit. This is often written as T² ∝ a³.

Question 2

#2

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23 Jan 2026

If a fixed amount of ideal gas has its absolute temperature doubled and volume halved, what change occurs in its pressure?

Answer

This problem is solved using the Combined Gas Law, P1V1/T1 = P2V2/T2, for a fixed amount of gas (n is constant). If the absolute temperature (T) is doubled (T2 = 2T1) and the volume (V) is halved (V2 = 0.5V1), the final pressure (P2) is calculated as P2 = P1 (V1/V2) (T2/T1) = P1 (V1 / 0.5V1) (2T1 / T1) = P1 2 2 = 4P1. The pressure quadruples.

Question 3

#3

By TheQuizWire

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Hard

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23 Jan 2026

What is the key factor determining a collapsing massive star’s fate: neutron star or black hole?

Answer

The final fate of a massive star (forming a neutron star or a black hole) is primarily determined by the mass of the compact remnant core after the supernova explosion and significant mass loss. If the remnant core's mass exceeds the Tolman-Oppenheimer-Volkoff (TOV) limit (approx. 2.1 to 3.0 solar masses), the internal pressure (neutron degeneracy pressure) is insufficient to resist gravity, leading to the formation of a black hole. If the core mass is below this limit, it stabilizes as a neutron star.

Question 4

#4

By TheQuizWire

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Hard

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23 Jan 2026

The Second Law of Thermodynamics fundamentally limits the efficiency of which process?

Answer

The Second Law of Thermodynamics (specifically the Kelvin-Planck statement) states that it is impossible to construct a device that operates in a cycle and produces no effect other than the extraction of heat from a reservoir and the performance of an equivalent amount of work. This fundamentally limits the maximum possible efficiency (Carnot efficiency) for converting heat energy into mechanical work.

Question 5

#5

By TheQuizWire

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Medium

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23 Jan 2026

What is the expected phenotypic ratio of offspring from a monohybrid cross between two heterozygous parents?

Answer

A monohybrid cross between two heterozygous parents (e.g., Bb x Bb) results in offspring with a genotypic ratio of 1 (BB): 2 (Bb): 1 (bb). Assuming B is dominant, the offspring will exhibit two phenotypes: the dominant trait (BB and Bb) and the recessive trait (bb). This combination yields the classic Mendelian phenotypic ratio of 3:1.

Question 6

#6

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Medium

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22 Jan 2026

A deep trench, a volcanic arc, and deep earthquakes best indicate which type of tectonic plate boundary?

Answer

The simultaneous presence of a deep oceanic trench (where the denser plate sinks), a volcanic arc (formed by the melting of the mantle wedge above the subducting slab), and deep-focus earthquakes (caused by the sinking slab) is the definitive signature of an oceanic-continental convergent boundary, or subduction zone.

Question 7

#7

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Medium

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19 Jan 2026

What is the primary function of ribosomes within a cell?

Answer

Ribosomes are essential cellular structures known as the 'protein factories' of the cell. Their primary function is to synthesize proteins through the process of translation, which uses the genetic information carried by mRNA.

Question 8

#8

By TheQuizWire

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19 Jan 2026

What two stellar properties are primarily related and plotted on the Hertzsprung-Russell (H-R) diagram?

Answer

The Hertzsprung-Russell (H-R) diagram is a pivotal tool in astronomy that visually represents the relationship between a star's intrinsic brightness, or luminosity (vertical axis), and its surface temperature, or spectral type/color index (horizontal axis). It is fundamental for understanding stellar evolution.

Question 9

#9

By TheQuizWire

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Medium

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19 Jan 2026

Which layer of the Earth is primarily a liquid alloy of iron and nickel?

Answer

The Outer Core is the layer of the Earth composed of molten iron and nickel, which is responsible for generating the Earth's magnetic field through convection currents. The Inner Core is solid.

Question 10

#10

By TheQuizWire

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Easy

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19 Jan 2026

What subatomic particle’s number uniquely defines an element and is its atomic number?

Answer

The atomic number (Z) of an element is defined by the number of protons in the nucleus. Changing the number of protons changes the element itself. The number of neutrons can change to form an isotope, and the number of electrons can change to form an ion, neither of which changes the fundamental identity (element) of the atom.

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