Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.There are several types of friction:

• Dry friction is a force that opposes the relative lateral motion of two solid surfaces in contact. Dry friction is subdivided into static friction between non-moving surfaces, and kinetic friction between moving surfaces. With the exception of atomic or molecular friction, dry friction generally arises from the interaction of surface features, known as asperities

• Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other.

• Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces.

• Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body.

• Internal friction is the force resisting motion between the elements making up a solid material while it undergoes deformation

Bryophytes are an informal group consisting of three divisions of non-vascular land plants (embryophytes), the liverworts, hornworts and mosses. They are characteristically limited in size and prefer moist habitats although they can survive in drier environments. The bryophytes consist of about 20,000 plant species. Bryophytes produce enclosed reproductive structures (gametangia and sporangia), but they do not produce flowers or seeds. They reproduce via spores. Bryophytes are usually considered to be a paraphyletic group and not a monophyletic group.

The defining features of bryophytes are:

• Their life cycles are dominated by the gametophyte stage

• Their sporophytes are unbranched

• They do not have a true vascular tissue containing lignin (although some have specialized tissues for the transport of water)

Charles Babbage was an English polymath. A mathematician, philosopher, inventor and mechanical engineer, Babbage originated the concept of a digital programmable computer.

The word “sovereign” described in the Preamble of the Constitution means that India is free from any force outside and is a solely supreme authority over all the citizens and institutions.

Mosses are non-vascular plants that do not have flowers or seeds. These simple plants typically grow in damp areas such as forests or wetlands. As for the life cycle of these plants, mosses are unique because they spend most of their lives with only one set of genetic material rather than the normal two sets. This would be like living the majority of your life cycle with only half of your genetic information.

The construction work on Jewar airport in Greater Noida will commence in December next year. It will start earlier than the Uttar Pradesh government's scheduled plan and well ahead of 2019 Lok Sabha elections. The Jewar airport is billed to become the biggest airport in India in terms of area.

The population growth curve will typically follow three key stages – an exponential growth phase, a transitional phase and a plateau phase. In plateau phase increasing mortality rate equals the natality rate and population growth becomes static.

The major festival of Kerala is Onam, Kuchipudi is the dance from of Andhra Pradesh, Pongal is a festival of Tamil Nadu and Gudipadwa is a main festival in Maharshtra.

The Indus Valley Civilisation or Harappan Civilisation was a Bronze Age civilisation mainly in the northwestern regions of South Asia, extending from what today is northeast Afghanistan to Pakistan and northwest India. Dancing Girl is a prehistoric bronze sculpture made in approximately 2500 BCE in the Indus Valley Civilisation city of Mohenjo-daro (in modern-day Pakistan), which was one of the earliest human cities.