Explanation

• Power is the rate of doing work or the rate at which energy is transferred.
• It is a scalar quantity (has magnitude only).
• It shows how quickly work is done.
• The SI unit of power is the Watt (W).
• 1 Watt = 1 Joule per second (1 W = 1 J/s).

Additional information:

• Formula: P = W/t = E/t
• SI Base Unit: kg·m²·s⁻³
• Dimension Formula: ML²T⁻³
• James Watt is the scientist after whom the Watt unit is named.

Last verified on 09-07-2026

Explanation

• A black hole has an extremely strong gravitational field.
• Its gravity is so powerful that even light cannot escape from it.
• Black holes are formed when very massive stars collapse after exhausting their fuel.
• The boundary beyond which nothing can escape is called the event horizon.
• The idea of black holes comes from Einstein's General Theory of Relativity (1915).

Last verified on 08-07-2026

Explanation

• Sputnik-1 was launched by the USSR (Soviet Union) on 4 October 1957.
• It was the world's first artificial satellite, beginning of the Space Age.
• It started the Space Race between the Soviet Union and the United States.
• Launch Site: Baikonur Cosmodrome, Kazakhstan
• Weight: 83.6 kg
• Orbital Period: About 96 minutes

Last verified on 09-03-2026

Explanation

• Rear view mirrors in vehicles are convex mirrors.
• They give a wider field of view.
• Images formed are virtual, upright, and smaller.
• This helps drivers see more traffic behind them.
• It is a curved mirror that bulges outward.
• It is commonly used in side mirrors of cars, buses, and motorcycles.

Last verified 26-04-2026

Explanation

• Silver reflects approximately 95% of visible light.
• It is one of the best natural reflectors of visible light.
• Because of its high reflectivity.
• Silver is widely used in mirrors and optical instruments.
• It produces bright and clear reflections.

Last verified on 07-06-2026