Explanation

• Cause: Mainly due to sulfur dioxide (SO₂) released from burning fossil fuels like coal and oil.
• Effect: SO₂ reacts with water vapor in the atmosphere to form sulfuric acid, causing acid rain.

Last verified on 08-02-2026

Explanation

• 1 Nanometer (nm) = 10⁻⁹ m (1 × 10⁻⁹ m)

Additional information:

• 1 Kilometer (km) = 10³ m
• 1 Meter (m) = 10⁰ m
• 1 Millimeter (mm) = 10⁻³ m
• 1 Micrometer (µm) = 10⁻⁶ m

Last verified on 06-07-2026

Explanation

• Gaps are provided between railway rails to allow for thermal expansion during hot weather.
• Metal rails expand when their temperature increases and contract when their temperature decreases.

Additional information:

• Scientific principle: Expansion of solids due to heat
• Effect of excessive heat: Rails may buckle
• Effect of cooling: Rails contract

Last verified on 12-10-2026

Explanation

• Velocity is a vector quantity. 
• A vector quantity has both magnitude and direction.
• Velocity, which describes the rate of change of position in a specific direction.
• It needs both a magnitude (speed) and a direction to be fully defined. 
• Vector Quantities: Velocity, momentum, torque, acceleration.
• Scalar Quantities: Work, distance, speed, mass.

Last verified on 12-10-2026

Explanation

• Mars is known as the Red Planet due to its reddish appearance.
• Its surface contains iron oxide (rust) which gives it a red color.
• It is the 4th planet from the Sun in the solar system.
• Mars has two small moons: Phobos and Deimos.
• Mars is often called the “planet of future exploration”.

Last verified on 12-06-2026