General Science Previous Year Questions (PYQ) with Answers – Page 18

The vehicle goes 100 m east and 200√2 m south, and the straight-line distance between start and finish is √(100² + (200√2)²) = 300 m. Each leg starts from rest, so the distance covered is s = ½at².

In free fall all the potential energy turns into kinetic energy, so 625 J = ½ × 0.32 kg × v², which gives v = 62.5 m/s. First change the mass into kilograms: 320 g = 0.32 kg.

The car loses a momentum of 1000 kg × 20 m/s in 0.2 s, so the force is 20,000 ÷ 0.2 = 100,000 N, that is 100 kN.

By Newton's third law, the gravitational force that the first planet exerts on the second is equal and opposite to the force the second exerts on the first.

Both statements are true, and the second explains the first: infrared waves are called heat waves because water molecules, present in most materials, absorb them readily and heat up.

Heat is energy in transit: it flows from a hotter body to a colder one only because their temperatures differ, and stops when they reach the same temperature.

It takes most force to start an object moving, less to keep it sliding and least to keep it rolling.

The restoring force on the bob is mg sin θ. For small angles sin θ is almost equal to θ, so the force becomes proportional to the displacement and points back towards the mean position.

Myopia is short-sightedness: near objects look sharp but distant ones look blurred. In a myopic eye the eyeball is too long or the eye lens is too curved, so light from a distant object comes to a focus in front of the retina instead of on it.

Cetane is the common name of n-hexadecane, C16H34, a straight-chain alkane with sixteen carbon atoms. Cetane ignites very readily when compressed, which is exactly what a diesel engine needs, because diesel fuel is not lit by a spark but catches fire from the heat of compressed air.

Sound in liquids and gases travels as a longitudinal wave, not a transverse one. In a longitudinal wave the particles of the medium vibrate back and forth along the direction in which the wave moves, forming compressions and rarefactions.

Light from an object at the centre of curvature strikes a concave mirror along its radius, so it returns along the same path and forms the image at the same point.

Sponges belong to the phylum Porifera, a name that means "pore bearers", because their bodies are full of tiny pores.

In the liver, methanol is oxidised to methanal (formaldehyde), which coagulates protoplasm and damages cells. Methanol, CH3OH, is the simplest alcohol and is sometimes mixed into illicit liquor.

This follows the order of these metals in the reactivity series, and hydrochloric acid reacts fastest with the metal highest in it.

DNA copies itself from loosened chromatin, and chromatin condenses into chromosomes before division, but prokaryotes divide differently from eukaryotes. In a non-dividing eukaryotic cell, DNA lies in the nucleus as a loose network called chromatin.

Bronchioles are the fine branches of the airways in the lungs, and their walls have no cartilage. Cartilage is a firm but flexible connective tissue.

A balanced diet contains all the nutrients the body needs, along with roughage and water, in the right amounts. Carbohydrates and fats give energy, proteins build and repair the body, and vitamins and minerals protect against disease and keep body processes running.

Aluminium oxide reacts with both acids and bases to form salt and water, which is what makes an oxide amphoteric.

Living things are built up level by level: molecules such as proteins form cells, cells form tissues, tissues form organs, organs form organ systems, and these together make an organism.