Explanation

Sound travels faster in solids than in liquids and gases due to the closer arrangement of particles in solids.

Iron, being a solid, allows sound to travel faster compared to air and water.

Explanation

The cordless power tools were developed during the Apollo missions to collect and study moon soil samples.

These tools helped astronauts drill into the lunar surface and bring back samples without power cords, making them more practical in space.

Explanation

Galaxies are the basic building blocks of the universe, consisting of stars, gas, dust, and dark matter.

The universe contains billions of galaxies, each with millions or billions of stars.

Explanation

Edwin Hubble's observations of galaxies moving away from each other, encapsulated in Hubble's Law, were crucial in suggesting that the universe is expanding.

This observation strongly supported the idea that the universe had a singular, hot, dense origin.

Georges Lemaître, in 1927, was the first to propose the idea of the universe expanding from a "primeval atom," a concept that would later form the basis of the Big Bang theory.

Explanation

A periscope is used to see objects above the eye level, commonly in submarines or behind obstacles.

It uses mirrors or prisms to reflect light down to the viewer’s eyes.

Explanation

Explanation

A fuse is a thin wire that melts and breaks the circuit if too much current flows, protecting appliances.

It acts as a safety device to prevent damage from overheating or short circuits.

Explanation

In the temperate zone, the sun’s rays fall at a slant angle, not directly overhead.

This results in milder temperatures compared to the tropical zone.

Explanation

The area of a circular sector is given by the formula:

Area = (1/2) × r² × θ

where r is the radius and θ is the angle in radians.

This formula applies only when θ is in radians.

Explanation

Ohm's Law states that voltage (V) is equal to the product of current (I) and resistance (R):

V = I × R

This law helps calculate the third quantity when any two (voltage, current, resistance) are known.