Physics

The damping in a simple pendulum is primarily caused by the drag force of air, which opposes the motion and gradually reduces the amplitude of oscillation. Gravity and tension in the string are forces that sustain the pendulum's motion rather than cause damping.

A lens that converges parallel rays of light to a single point is called a converging lens, which is typically convex in shape. This is because convex lenses bend light rays inward to meet at the focal point.

Albert Einstein proposed the concept of the photon as a quantum of light in 1905, explaining the photoelectric effect and introducing the idea that light can be quantized into discrete packets called photons.

Simple Harmonic Motion (S.H.M.) produces a sinusoidal waveform because the displacement varies sinusoidally with time, characteristic of oscillatory motion governed by sine or cosine functions.

The density of human blood is close to that of water, approximately 1.06 g/cm³, making water the best comparison among the options given. Honey, mercury, and kerosene have significantly different densities.

In angular motion, Newton's second law is expressed as the net torque (Στ) equals the moment of inertia (I) times the angular acceleration (α), which is option C. Option A is the linear form of Newton's second law, and option B is incorrect. Therefore, option C correctly represents Newton's second law for rotational motion.

To cover the entire Earth continuously with communication satellites, at least three satellites are needed in geostationary orbit spaced evenly around the equator. This allows overlapping coverage ensuring no area is left uncovered.

The critical speed (orbital velocity) for a satellite near Earth's surface is approximately 8.1 km/s. Option B (8.1 Kms-1) is the most accurate value among the given choices. Other options are either slightly off or incorrect units.

Bernoulli's equation is derived by applying the law of conservation of energy to a flowing fluid, relating pressure, velocity, and height along a streamline.

A chimney works best when the air outside is moving because moving air creates a pressure difference that helps draw smoke and gases up and out of the chimney, improving draft efficiency.