General Science Previous Year Questions (PYQ) with Answers – Page 68

In ferric oxide both iron atoms are in the same +3 oxidation state. In Fe₂O₃ three oxide ions carry a total charge of −6, shared equally by two iron atoms, so each iron is +3.

Momentum is a vector, and on bouncing the ball's direction of motion reverses at once, from downward to upward. Just before impact the ball moves down with velocity v, so its momentum is mv downward.

High pressure pushes the gas molecules close together and low temperature slows them down, so the attractive forces can hold them as a liquid.

Methanol (CH3OH) is called wood spirit or wood alcohol because it was first obtained by the destructive distillation of wood.

Marsilea is a water fern, a pteridophyte, and pteridophytes are the first land plants with true vascular tissues, xylem and phloem.

The pericycle is a layer of cells around the vascular cylinder of the root and stem; it is not part of xylem or phloem.

Radiant heat is infrared electromagnetic radiation, so it travels in straight lines at the speed of light. Heat moves in three ways.

The anther is the top part of the stamen, the male organ of a flower, and pollen grains form inside it.

A large central vacuole filled with sap presses the cytoplasm against the cell wall, keeping the cell firm, or turgid.

Apical meristem sits at the growing tips of stems and roots, and its dividing cells make them longer. Meristems are groups of cells that keep dividing throughout a plant's life.

Ribosomes stuck on the outer surface of the endoplasmic reticulum give it a grainy, rough look under the electron microscope.

A medium more concentrated than the cell is hypertonic, so water leaves the cell by osmosis. In osmosis water moves across a selectively permeable membrane from the side with fewer dissolved particles to the side with more.

A ribosome contains RNA, but it has no genes of its own; it reads messenger RNA sent from the DNA of the nucleus or an organelle.

A chemical reaction produces only internal forces, which cannot change the motion of the centre of mass but can change internal kinetic energy.

The plasma membrane is made of lipids and proteins and contains no DNA or RNA. The plasma membrane is the outer boundary of the cell.

Rotational kinetic energy is ½Iω², and the ring has the larger moment of inertia. For a thin ring about the axis through its centre and perpendicular to its plane, all the mass sits at distance R, so I = MR².

An adult set of thirty-two permanent teeth has eight incisors for cutting, four canines for tearing, eight premolars and twelve molars for grinding, so there is one canine on each side of each jaw.

It is a thin, strap-like muscle that runs across the front of the thigh from the hip bone to the inner side of the knee, and because it crosses two joints it is the longest muscle of the human body; it helps in bending the hip and the knee and…

A bacterium is a living cell filled with cytoplasm, while a virus is only genetic material inside a protein coat.

Chlamydomonas is a unicellular, flagellated member of the Chlorophyceae, the green algae, in which chlorophyll a and b give the plant its grass-green colour and the food is stored as starch.