Explanation

The color of a star is directly related to its temperature.

Hotter stars appear blue or white, while cooler stars appear red.

Explanation

• Clouds float in the atmosphere because they are less dense than the surrounding air. Clouds are formed when water vapor in the air condenses into visible liquid droplets or ice crystals. These droplets or crystals are suspended in the air, and because they are less dense than the air, they float.
• The density of a cloud is typically around 0.05-0.5 g/m³, which is much less than the density of air, which is around 1.2 g/m³. This density difference allows clouds to remain suspended in the air, even though they are heavier than air in terms of their mass.

Explanation

Telstar was the first TV relay satellite launched into space by the United States on July 10, 1962.

It enabled the first transatlantic television transmission, revolutionizing global communication.

Explanation

• 1 second → Half oscillation of a seconds pendulum
• 0.1 second → Very fast oscillating system
• 2 seconds → Time period of a seconds pendulum
• 0.5 second → Faster pendulum, shorter length than seconds pendulum

Explanation

Sand particles are generally grey in color, though they can vary depending on their mineral content.

They are light in weight and have larger, coarse grains compared to silt or clay.

Explanation

The speed of sound in water is approximately 1500 m/s, which is slower than in most solid materials but faster than in air.

This speed can vary slightly depending on factors like temperature and salinity.

Explanation

Gears work on the principle of transmitting rotational force from one gear to another.

This helps in changing the speed, direction, or torque in a mechanical system.

Explanation

Heat transfer occurs through conduction, convection, and radiation.

Condensation is a phase change process (gas to liquid).

It is not a heat transfer method.

Explanation

Non-renewable energy sources:

• Oil
  
• Nuclear energy
• Petroleum
• Natural gas & coal

Renewable sources of energy:

• Solar energy
• Wind energy
• Hydroelectric power
• Biomass energy
• Geothermal energy
• Tidal energy

Explanation

Potential energy and kinetic energy are types of mechanical energy. 

Mechanical energy encompasses both potential energy (stored energy due to position) and kinetic energy (energy of motion).